Numerical simulations of near-field head-related transfer functions: Magnitude verification and validation with laser spark sources.

Despite possessing an increased perceptual significance, near-field head-related transfer functions (nf-HRTFs) are more difficult to acquire compared to far-field head-related transfer functions. If properly validated, numerical simulations could be employed to estimate nf-HRTFs: the present study aims to validate the usage of wave-based simulations in the near-field. A thorough validation study is designed where various sources of error are investigated and controlled. The present work proposes the usage of a highly-omnidirectional laser-induced breakdown (LIB) of air as an acoustic point source in nf-HRTF measurements. Despite observed departures from the linear regime of the LIB pressure pulse, the validation results show that asymptotically-estimated solutions to a lossless model (wave-equation and rigid boundaries) agree in magnitude with the LIB-measured nf-HRTF of a rigid head replica approximately within 1-2 dB up to about 17 kHz. Except a decreased reliability in notch estimation, no significant shortcoming of the continuous model is found relative to the measurements below 17 kHz. The study also shows the difficulty in obtaining accurate surface boundary impedance values for accurate validation studies.

Emergency Surgery in Urology during the COVID-19 Pandemic.

Proposal: To highlight the indications for emergency surgery during the 2019 Coronavirus pandemic (COVID-19) that support recommendations published in mid-March 2020 by the American Confederation of Urology on its website. MATERIALS AND METHODS: A bibliographic search was conducted in PubMed and Cochrane Library to perform a non-systematic review, using key words: Urology, Emergency and COVID-19, to determine recommendations for patients that should receive emergency care due to urological pathology. RESULTS: The main recommendations and protocols in the management of different urological emergencies during the COVID-19 pandemic are reviewed and discussed. CONCLUSIONS: We are living a new condition with the COVID-19 pandemic, which obliges urologists to conform to the guidelines that appear on a daily basis formulated by multidisciplinary surgical groups to manage urological emergencies. Consequently, in this time of health crisis, we must adapt to the resources available, implementing all biosecurity measures to protect patients and all health personnel who are in charge of patient management.

Emergency Surgery in Urology during the COVID-19 Pandemic

ABSTRACT Proposal: To highlight the indications for emergency surgery during the 2019 Coronavirus pandemic (COVID-19) that support recommendations published in midMarch 2020 by the American Confederation of Urology on its website. Materials and Methods: A bibliographic search was conducted in PubMed and Cochrane Library to perform a non-systematic review, using key words: Urology, Emergency and COVID-19, to determine recommendations for patients that should receive emergency care due to urological pathology. Results: The main recommendations and protocols in the management of different urological emergencies during the COVID-19 pandemic are reviewed and discussed. Conclusions: We are living a new condition with the COVID-19 pandemic, which obliges urologists to conform to the guidelines that appear on a daily basis formulated by multidisciplinary surgical groups to manage urological emergencies. Consequently, in this time of health crisis, we must adapt to the resources available, implementing all biosecurity measures to protect patients and all health personnel who are in charge of patient management.

Pinna-related transfer functions and lossless wave equation using finite-difference methods: Validation with measurements.

Nowadays, wave-based simulations of head-related transfer functions (HRTFs) lack strong justifications to replace HRTF measurements. The main cause is the complex interactions between uncertainties and biases in both simulated and measured HRTFs. This paper deals with the validation of pinna-related high-frequency information in the ipsilateral directions-of-arrival, computed by lossless wave-based simulations with finite-difference models. A simpler yet related problem is given by the pinna-related transfer function (PRTF), which encodes the acoustical effects of only the external ear. Results stress that PRTF measurements are generally highly repeatable but not necessarily easily reproducible, leading to critical issues in terms of reliability for any ground truth condition. On the other hand, PRTF simulations exhibit an increasing uncertainty with frequency and grid-dependent frequency changes, which are here quantified analyzing the benefits in the use of a unique asymptotic solution. In this validation study, the employed finite-difference model accurately and reliably predict the PRTF magnitude mostly within ±1 dB up to ≈8 kHz and a space- and frequency-averaged spectral distortion within about 2 dB up to ≈ 18 kHz.

Implementation Analysis of a Perioperative Patient Safety Program in Guatemala.

BACKGROUND: The implementation of programs to improve patient safety remains challenging in low- and middle-income countries. The goal of our study was to define the barriers and facilitators to implementation of a perioperative patient safety program in Guatemala. MATERIAL AND METHODS: We conducted semi-structured interviews with 16 staff pre-intervention and a follow-up focus group discussion 1 year later in the perioperative department at the Roosevelt Hospital in Guatemala. We performed qualitative thematic analysis to identify barriers and facilitators to the implementation process, with analysis guided by the Consolidated Framework for Implementation Research. RESULTS: We found several dominant themes affecting implementation of a patient safety program. Implementation facilitators included strong prioritization of patient needs, program compatibility with existing workflow, and staff attributes. Barriers included a lack of knowledge about patient safety, limited resources, limited leadership engagement, and lack of formal implementation leaders. Several program modifications were made to enhance successful implementation iteratively during the implementation process. DISCUSSION: Our analysis highlights several dominant themes which affect the implementation of a perioperative safety program in Guatemala. Understanding the barriers and facilitators to implementation during program deployment allows for program modification and improvement of the implementation process itself.

Pinna-related transfer functions and lossless wave equation using finite-difference methods: Verification and asymptotic solution.

A common approach when employing discrete mathematical models is to assess the reliability and credibility of the computation of interest through a process known as solution verification. Present-day computed head-related transfer functions (HRTFs) seem to lack robust and reliable assessments of the numerical errors embedded in the results which makes validation of wave-based models difficult. This process requires a good understanding of the involved sources of error which are systematically reviewed here. The current work aims to quantify the pinna-related high-frequency computational errors in the context of HRTFs and wave-based simulations with finite-difference models. As a prerequisite for solution verification, code verification assesses the reliability of the proposed implementation. In this paper, known and manufactured formal solutions are used and tailored for the wave equation and frequency-independent boundary conditions inside a rectangular room of uniform acoustic wall-impedance. Asymptotic estimates for pinna acoustics are predicted in the frequency domain based on regression models and a convergence study on sub-millimeter grids. Results show an increasing uncertainty with frequency and a significant frequency-dependent change among computations on different grids.

Benefits and applications of laser-induced sparks in real scale model measurements.

The characteristics of using a laser-induced spark as a monopole source in scale model measurements were assessed by comparison with an electric spark and a miniature spherical loudspeaker. Room impulse responses of first order directivity sources were synthesized off-line using six spatially distributed sparks. The source steering direction was scanned across the horizontal and vertical plane to assess the origin of early reflections. The results confirm that the characteristics of the laser-induced spark outperform those of typical sources. Its monopole characteristics enable the authors to synthesize room responses of directional sources, e.g., to obtain directional information about reflections inside scale models.

Beamforming with a volumetric array of massless laser spark sources--Application in reflection tracking.

A volumetric array of laser-induced air breakdown sparks is used to produce a directional and steerable acoustic source. The laser breakdown array element is broadband, point-like, and massless. It produces an impulse-like waveform in midair, thus generating accurate spatio-temporal information for acoustic beamforming. A laser-spark scanning setup and the concept of a massless steerable source are presented and evaluated with a cubic array by using an off-line far field delay-and-sum beamforming method. This virtual acoustic array with minimal source influence can, for instance, produce narrow transmission beams to obtain localized and directional impulse response information by reflection tracking.

Laser-induced acoustic point source for accurate impulse response measurements within the audible bandwidth.

Laser induced air breakdown is proposed as a sound source for accurate impulse response measurements. Within the audible bandwidth, the source is repeatable, broadband, and omnidirectional. The applicability of the source was evaluated by measuring the impulse response of a room. The proposed source provides a more accurate temporal and spatial representation of room reflections than conventional loudspeakers due to its omnidirectionality, negligible size and short pulse duration.

An optoacoustic point source for acoustic scale model measurements.

A massless acoustic source is proposed for scale model work. This source is generated by focusing a pulsed laser beam to rapidly heat the air at the focal point. This produces an expanding small plasma ball which generates a sonic impulse that may be used as an acoustic point source. Repeatability, frequency response, and directivity of the source were measured to show that it can serve as a massless point source. The impulse response of a rectangular space was determined using this type of source. A good match was found between the predicted and the measured impulse responses of the space.

Casos quirúrgicos relevantes: separación de gemelos siameses thoraco-omphalopagus en Guatemala / Separation of thoraco-omphalopagus siamese twins in Guatemala

Este reporte describe la separación de gemelos siameses Thoraco-omphalopagus y su manejo. ambas siameses compartían el hígado y la bolsa pericárdica y se encontraban unidas desde el tórax, en el manubrio esternal hasta su inserción baja del ombligo en el abdomen. Se describen sus estudios pre-operatorios de TAC y RMI demostrando la presencia de una arteria nutricia que atravesaba el hígado de la gemela A a la B la cual alimentaba a esta última, quien además presentaba un corazón rudimentario con la presencia de solamente una aurícula y un ventrículo.