Orthogonal Orientations Research Articles

Goblet cell interactions reorient bundled mucus strands for efficient airway clearance.

The respiratory tract of larger animals is cleared by sweeping bundled strands along the airway surface. These bundled strands can be millimetric in length and consist of MUC5B mucin. They are produced by submucosal glands, and upon emerging from these glands, the long axis of the bundled strands is oriented along the cilia-mediated flow toward the oral cavity. However, after release, the bundled strands are found to have turned orthogonal to the flow, which maximizes their clearance potential. How this unexpected reorientation is accomplished is presently not well understood. Recent experiments suggest that the reorientation process involves bundled strands sticking to MUC5AC mucus threads, which are tethered to the goblet cells. Such goblet cells are present in small numbers throughout the airway epithelium. Here, we develop a minimal model for reorientation of bundled mucus strands through adhesive interactions with surface goblet cells. Our simulations reveal that goblet cell interactions can reorient the bundled strands within 10 mm of release-making reorientation on the length scale of the tracheal tube feasible-and can stabilize the orthogonal orientation. Our model also reproduces other experimental observations such as strong velocity fluctuations and significant slow-down of the bundled strand with respect to the cilia-mediated flow. We further provide insight into the strand turning mechanism by examining the effect of strand shape on the impulse exerted by a single goblet cell. We conclude that goblet cell-mediated reorientation is a viable route for bundled strand reorientation, which should be further validated in future experiment.

Electroanatomical voltage mapping with contact force sensing for diagnosis of arrhythmogenic right ventricular cardiomyopathy

BackgroundThree-dimensional electroanatomical mapping (EAM) can be helpful to diagnose arrhythmogenic right ventricular cardiomyopathy (ARVC). Yet, previous studies utilizing EAM have not systematically used contact-force sensing catheters (CFSC) to characterize the substrate in ARVC, which is the current gold standard to assure adequate tissue contact. ObjectiveTo investigate reference values for endocardial right ventricular (RV) EAM as well as substrate characterization in patients with ARVC by using CFSC. MethodsEndocardial RV EAM during sinus rhythm was performed with CFSC in 12 patients with definite ARVC and 5 matched controls without structural heart disease. A subanalysis for the RV outflow tract (RVOT), septum, free-wall, subtricuspid region, and apex was performed. Endocardial bipolar and unipolar voltage amplitudes (BVA, UVA), signal characteristics and duration as well as the impact of catheter orientation on endocardial signals were also investigated. ResultsARVC patients showed lower BVA vs. controls (p = 0.018), particularly in the subtricuspid region (1.4, IQR:0.5–3.1 vs. 3.8, IQR:2.5-5 mV, p = 0.037) and RV apex (2.5, IQR:1.5–4 vs. 4.3,IQR:2.9–6.1 mV, p = 0.019). BVA in all RV regions yielded a high sensitivity and specificity for ARVC diagnosis (AUC 59–78%, p < 0.05 for all), with the highest performance for the subtricuspid region (AUC 78%, 95% CI:0.75–0.81, p < 0.001, negative predictive value 100%). A positive correlation between BVA and an orthogonal catheter orientation (46°-90°:r = 0.106, p < 0.001), and a negative correlation between BVA and EGM duration (r = −0.370, p < 0.001) was found. ConclusionsEAM using CFSC validates previous bipolar cut-off values for normal endocardial RV voltage amplitudes. RV voltages are generally lower in ARVC as compared to controls, with the subtricuspid area being commonly affected and having the highest discriminatory power to differentiate between ARVC and healthy controls. Therefore, EAM using CFSC constitutes a promising tool for diagnosis of ARVC.

First-principles study on the upper pressure limit of diamond under multiaxial stress

In this study, we investigated the upper pressure limit of diamond. A method for predicting the upper pressure limit of diamonds under multiaxial stress is developed by introducing stress angles α based on first-principles calculations. The normal stresses of diamond in three mutually orthogonal orientations [111], 112¯, and 11¯0 are set as σ111tanα=σ112¯=σ11¯0. The three most important characteristics, namely, the theoretical strength, maximum dynamic stability stress, and phase transition stress, are evaluated and analysed to further determine the upper pressure limit of diamond. The calculated results indicate that the upper pressure limit of diamond can reach up to 1.265 TPa in the [111] orientation under multiaxial compressions, which is approximately 1.25 times higher than that of our calculated phase transition stress (σ[111] = 1008.3 GPa) and 1.18–1.28 times higher than that of the current upper pressure limit 990 (Phys. Rev. Lett. 108 (2012) 045704)–1075 GPa (Proc. Natl Acad. Sci. U. S. A. 103 (2006) 1204) at a hydrostatic pressure, which is a new record. This study provides a possible approach to obtain a high pressure limit by multiaxial compression, which will advance the progress of in-situ high-pressure anvil technology.

Investigation of the Features of a Superconducting Spin Valve Fe1/Cu/Fe2/Cu/Pb on a Piezoelectric PMN–PT Substrate

The properties of a superconducting spin valve Fe1/Cu/Fe2/Cu/Pb on a piezoelectric PMN–PT substrate ([Pb(Mg1/3Nb2/3)O3]0.7–[PbTiO3]0.3) in electric and magnetic fields have been studied. The magnitude of the shift of the superconducting transition temperature in the magnetic field H = 1 kOe equal to 150 mK was detected, while the full superconducting spin valve effect was demonstrated. Abnormal behavior of the superconducting transition temperature was observed, which manifests itself in the maximum values of the superconducting transition temperature with the orthogonal orientation of the magnetization vectors of ferromagnetic layers. This may indirectly indicate the formation of the easy axis of the magnetization vector of the Fe1-layer adjacent to the piezoelectric substrate PMN–PT. It was found that with an increase in the magnitude of the applied electric field to the PMN–PT substrate, the shift in the superconducting transition temperature of the Fe1/Cu/Fe2/Cu/Pb heterostructure increases. The maximum shift was 10 mK in an electric field of 1 kV/cm. Thus, it has been shown for the first time that a piezoelectric superconducting spin valve can function.

Acute exercise has specific effects on the formation process and pathway of visual perception in healthy young men.

Visual perception is formed over time through the formation process and visual pathway. Exercise improves visual perception, but it is unclear whether exercise modulates nonspecifically or specifically the formation process and pathway of visual perception. Healthy young men performed the visual detection task in a backward masking paradigm before and during cycling exercise at a mild intensity or rest (control). The task presented gratings of a circular patch (target) and annulus (mask) arranged concentrically as a visual stimulus and asked if the presence and striped pattern (feature) of the target were detected. The relationship between the orientations of the gratings of the target and the mask included iso-orientation and orthogonal orientation to investigate the orientation selectivity of the masking effect. The masking effect was evaluated by perceptual suppressive index (PSI). Exercise improved feature detection (∆PSI; Exercise: -20.6%, Control: 1.7%) but not presence detection (∆PSI; Exercise: 8.9%, Control: 29.6%) compared to the control condition, and the improving effect resulted from the attenuation of the non-orientation-selective (∆PSI; Exercise: -29.0%, Control: 16.8%) but not orientation-selective masking effect (∆PSI; Exercise: -3.1%, Control: 11.7%). These results suggest that exercise affects the formation process of the perceptual feature of the target stimulus by suppressively modulating the neural networks responsible for the non-orientation-selective surround interaction in the subcortical visual pathways, whose effects are inherited by the cortical visual pathways necessary for perceptual image formation. In conclusion, our findings suggest that acute exercise improves visual perception transiently through the modulation of a specific formation process of visual processing.

How far does electrical stimulation activate white matter tracts? A computational modeling study

ObjectiveThe aim of this study was to model how the different parameters of electrical stimulation (intensity, pulse shape, probe geometry) influence the extent of white matter activation. MethodsThe electrical potentials generated by the stimulating electrodes were determined by solving Laplace equation. The temporal evolution of membrane potentials at each nodes of Ranvier of an axon was then computed by solving the coupled system of differential equations describing membrane dynamics and cable propagation. ResultsRegions of unilateral propagation were observed for monophasic pulses delivered with a bipolar probe aligned along the tract. For biphasic pulses, the largest activation areas and depths were found with a high inter-electrode-distance (IED) bipolar probe, oriented orthogonally to the tract. The smallest activation areas and depths were found for bipolar stimulations with the probe aligned parallel to the tract and low IED. For isotropic white matter regions, the activation area and depth were three times larger than for anisotropic white matter tracts. ConclusionsBipolar probes with biphasic pulses offer the greatest versatility: an orthogonal orientation acts as two monopolars (increased sensitivity when searching for a tract), whereas a parallel orientation corresponds to a single monopolar (increased specificity). Activation is more superficial when stimulating highly anisotropic tracts. SignificanceThis knowledge is essential for interpreting the behavorial effects of stimulation and the recordings of axono-cortical evoked potentials.

Enhanced perceptual selection of predicted stimulus orientations following statistical learning.

Perception is influenced by predictions about the sensory environment. These predictions are informed by past experience and can be shaped by exposure to recurring patterns of sensory stimulation. Predictions can enhance perception of a predicted stimulus, but they can also suppress it by favoring novel and unexpected sensory information that is inconsistent with the predictions. Here we employed statistical learning to assess the effects of exposure to consistent sequences of oriented gratings on subsequent visual perceptual selection, as measured with binocular rivalry. Following statistical learning, the first portion of a learned sequence of stimulus orientations was presented to both eyes, followed by simultaneous presentation of the next grating in the sequence to one eye and an orthogonal unexpected orientation to the other eye. We found that subjects were more likely to perceive the grating that matched the orientation that was consistent with the predictive context. That is, observers were more likely to see what they expected to see, compared to the likelihood of perceiving the unexpected stimulus. Some other studies in the literature have reported the opposite effect of prediction on visual perceptual selection, and we suggest that these inconsistencies may be due to differences across studies in the level of the visual processing hierarchy at which competing perceptual interpretations are resolved.

An interactive approach for generating spatial architecture layout based on graph theory

This study proposes a graph theory based method for generating three-dimensional architectural layouts on the target of creating space that provides rich perceptual experience. The proposed approach incorporates the decisions of architects in the generation process to improve efficiency and avoid invalid results. Space is interpreted as a combination of volumes adjacent to, intersecting with or containing each other and is represented by a graph with nodes and edges. The study first generates an orthogonal orientation digraph (OODG), which denotes the relative positions of spaces and provides options for users to decide whether to continue generating the layout. Based on a given OODG, a combination of connected volumes is generated. The generation results show that the proposed method can generate space providing a rich experience when relations between volumes are properly set.

Electroanatomical voltage mapping with a force-sensing technology catheter for diagnosis of Arrhythmogenic Right Ventricular Cardiomyopathy (ARVC)

Abstract Funding Acknowledgements Type of funding sources: None. Introduction Invasive three-dimensional electroanatomical mapping (EAM) can be helpful to diagnose arrhythmogenic right ventricular cardiomyopathy (ARVC). Contact force sensing catheters (CFSC) represent the gold standard to verify adequate tissue contact during EAM. However, normal reference values for right ventricular (RV) EAM as well as substrate characterization in patients with ARVC using CFSC have not been systematically investigated, which was the aim of this prospective study. Methods EAM of the RV during sinus rhythm was performed with the Thermocool SmartTouch catheter via a long sheath in the CARTO3 system in 11 patients with definite ARVC and 5 age- and gender-matched control subjects without structural heart disease. Only points with a mean contact force of ≥4G were analyzed. To account for differences due to RV anatomy, it was divided into 5 segments: RV outflow tract (RVOT), septum, free wall, sub-tricuspid region and apex. Endocardial bipolar and unipolar voltages, signal characteristics and signal duration were analyzed. The impact of catheter orientation on endocardial signals was also assessed. Results A median of 227 (IQR:120-364) endocardial RV points were analyzed. Median bipolar voltage in healthy controls was 3.8mV (range 3.6-4.6, IQR 2.7-5.4), with lower values in the RVOT and higher values in the RV septum. ARVC patients showed significantly lower bipolar voltages as compared to controls (repeated measures ANOVA; between-subjects effect: F=6.443,p=0.024), showing significantly lower bipolar voltage values in the sub-tricuspid region (1.8±1.9vs.4.6±2.9mV,p=0.031) and in the RV apex (2.9±1.4vs.7.2±5.2mV,p=0.024), Figure 1c. Bipolar voltage values in all RV regions yielded a high sensitivity and specificity for ARVC diagnosis (AUC62-78%,p&amp;lt;0.001 for all), with the highest performance for the sub-tricuspid region (AUC78%,95%CI0.75-0.81,p&amp;lt;0.001). A bipolar voltage value &amp;lt;1.5mV in the sub-tricuspid region yielded a sensitivity of 98% and a specificity of 53% for ARVC diagnosis (Figure 1a-b, showing the typical RV free wall "C-scar" in ARVC and normal values for the RV apex in less advanced disease stages). A positive correlation between bipolar voltage values and an orthogonal catheter orientation (46°-90°: r=0.106,p&amp;lt;0.001) as well as a higher catheter contact force (r=0.054,p=0.008), and a negative correlation between bipolar voltage values and QRS duration (r=-0.370,p&amp;lt;0.001) was found. Conclusions For the first time a systematic analysis of RV endocardial low voltage areas in ARVC patients as compared to controls by using CFSC was performed, and confirmed that RV voltages are generally lower in ARVC as compared to controls, with the sub-tricuspid area showing the lowest values and highest discriminatory power vs controls.

Van der Waals Heterostructure Mid-Infrared Emitters with Electrically Controllable Polarization States and Spectral Characteristics.

Modern infrared (IR) microscopy, communication, and sensing systems demand control of the spectral characteristics and polarization states of light. Typically, these systems require the cascading of multiple filters, polarization optics, and rotating components to manipulate light, inevitably increasing their sizes and complexities. Here, we report two-terminal mid-infrared (mid-IR) emitters, in which tuning the polarity of the applied bias can switch their emission peak wavelengths and linear polarization states along two orthogonal orientations. Our devices are composed of two back-to-back p-n junctions formed by stacking anisotropic light-emitting materials, black phosphorus and black arsenic-phosphorus with MoS2. By controlling the crystallographic orientations and engineering the band profile of heterostructures, the emissions of two junctions exhibit distinct spectral ranges and polarization directions; more importantly, these two electroluminescence (EL) units can be independently activated, depending on the polarity of the applied bias. Furthermore, we show that when operating our emitter under the polarity-switched pulse mode, the time-averaged EL exhibits the characteristics of broad spectral coverage, encompassing the entire first mid-IR atmospheric window (λ: 3-5 μm), and electrically tunable spectral shapes.

Crystal Structure, Hirshfeld Surface Analysis, and Computational Study of Quinolin-8-yl 4-Chlorobenzoate: Insights from Spectroscopic, Thermal, and Antitumor Properties

We report the time-efficient synthesis of quinolin-8-yl 4-chlorobenzoate (3) via an O-acylation reaction between 8-hydroxyquinoline (1) and 4-chlorobenzoyl chloride (2) mediated by triethylamine in acetonitrile under heating at 80 °C for 20 min in the Monowave 50 reactor. This protocol is distinguished by its short reaction time, operational simplicity, and clean reaction profile. The structure of 3 was fully characterized through a combination of analytical techniques, including NMR, IR, and UV–Vis spectroscopy, MS spectrometry, differential scanning calorimetry (DSC), thermogravimetry (TG), and crystallographic studies. Interestingly, X-ray diffraction analyses of 3 show that the crystal structure is characterized by C-H···N, C-H···O, Cl···π, and π···π interactions. The molecular conformation presents an orthogonal orientation between aromatic rings in the solid state. The calculated interaction energies using the CE-B3LYP model show that dispersion forces act in a higher proportion to build the crystal, which is consistent with the few short hydrogen interactions detected. Electrostatic potential maps suggest the formation of σ-holes over the Cl atoms. Although they can behave as both Lewis acid and base sites, Cl··Cl interactions are absent due to the shallow depth of these σ-holes. Quantum chemical descriptors and global reactivity descriptors were examined using the B3LYP method with the 6-31G(d,p) basis set implemented in CrystalExplorer. Finally, compound 3 exhibited low activity against HOP-92 and EKVX non-Small-cell lung and UO-31 Renal cancer cell lines, with a growth inhibition percentage (GI%) ranging from 6.2% to 18.1%.

Synthetic Model for FRET Constructed from Covalently Linked Porphyrin Dimers through a Pyrene Bridge.

We report the synthesis and characterization of two porphyrin arrays C6F5-PyZnDP and Mes-PyZnDP covalently linked by a pyrene moiety which differs from their substituents at their meso-positions. The key precursor bis-dipyrromethane linked with a pyrene bridge was prepared by the acid-catalyzed condensation of pyrene-1,6-dialdehyde with excess pyrrole. The synthesis of C6F5-PyZnDP was carried out via two different synthetic routes, with one being efficient over the other. Therefore, the superior route was employed for the synthesis of C6F5-PyZnDP and Mes-PyZnDP. Both the free base and metalated diporphyrins show bathochromically shifted absorption and intense red emission due to the extended π-conjugation through pyrene and porphyrins. The single-crystal X-ray structure reveals an orthogonal orientation of pyrene in between the two planar porphyrins and a slipped stacked packing arrangement in the crystal structure with large meso-meso distances. DFT analysis of both the ground state and the excited S1 state of the macrocycles indicates the difference in the HOMO and LUMO contribution in both the states arising from slight twisting from the mean orthogonal position in the excited state. Further, the Förster energy transfer (FRET) efficiencies from pyrene (donor) to the covalently linked Zn-porphyrins (acceptor) are estimated to be 85 and 91% for Mes-PyZnDP and C6F5-PyZnDP, respectively.

Topologically preoptimized ground structure (TPOGS) for the optimization of 3D RC buildings

As an optimization that starts from a randomly selected structure generally does not guarantee reasonable optimality, the use of a systemic approach, named the ground structure, is widely accepted in steel-made truss and frame structural design. However, in the case of reinforced concrete (RC) structural optimization, because of the orthogonal orientation of structural members, randomly chosen or architect-sketched framing is used. Such a one-time fixed layout trend, in addition to its lack of a systemic approach, does not necessarily guarantee optimality. In this study, an approach for generating a candidate ground structure to be used for cost or weight minimization of 3D RC building structures with included slabs is developed. A multiobjective function at the floor optimization stage and a single objective function at the frame optimization stage are considered. A particle swarm optimization (PSO) method is employed for selecting the optimal ground structure. This method enables generating a simple, yet potential, real-world representation of topologically preoptimized ground structure while both structural and main architectural requirements are considered. This is supported by a case study for different floor domain sizes.

Reconstruction algorithm using 2N+1 raw images for structured illumination microscopy.

This paper presents a structured illumination microscopy (SIM) reconstruction algorithm that allows the reconstruction of super-resolved images with 2N + 1 raw intensity images, with N being the number of structured illumination directions used. The intensity images are recorded after using a 2D grating for the projection fringe and a spatial light modulator to select two orthogonal fringe orientations and perform phase shifting. Super-resolution images can be reconstructed from the five intensity images, enhancing the imaging speed and reducing the photobleaching by 17%, compared to conventional two-direction and three-step phase-shifting SIM. We believe the proposed technique will be further developed and widely applied in many fields.

Textural Features of Mouse Glioma Models Measured by Dynamic Contrast-Enhanced MR Images with 3D Isotropic Resolution.

This paper investigates the effect of anisotropic resolution on the image textural features of pharmacokinetic (PK) parameters of a murine glioma model using dynamic contrast-enhanced (DCE) MR images acquired with an isotropic resolution at 7T with pre-contrast T1 mapping. The PK parameter maps of whole tumors at isotropic resolution were generated using the two-compartment exchange model combined with the three-site-two-exchange model. The textural features of these isotropic images were compared with those of simulated, thick-slice, anisotropic images to assess the influence of anisotropic voxel resolution on the textural features of tumors. The isotropic images and parameter maps captured distributions of high pixel intensity that were absent in the corresponding anisotropic images with thick slices. A significant difference was observed in 33% of the histogram and textural features extracted from anisotropic images and parameter maps, compared to those extracted from corresponding isotropic images. Anisotropic images in different orthogonal orientations demonstrated 42.1% of the histogram and textural features to be significantly different from those of isotropic images. This study demonstrates that the anisotropy of voxel resolution needs to be carefully considered when comparing the textual features of tumor PK parameters and contrast-enhanced images.

Reversibly switching liquid crystals between three orthogonal orientation states for use in rapid-response THz phase shifters.

Liquid crystal (LC) devices for terahertz phase shifters inevitably use a thick cell gap for the required retardation, severely delaying the LC response. To improve the response, we virtually demonstrate novel LC switching between in-plane and out-of-plane for reversible switching between three orthogonal orientation states, broadening the range of continuous phase shifts. This LC switching is realized using a pair of substrates, each with two pairs of orthogonal finger-type electrodes and one grating-type electrode for in- and out-of-plane switching. An applied voltage generates an electric field that drives each switching process between the three distinct orientation states, enabling a rapid response.

MOJAVE – XX. Persistent linear polarization structure in parsec-scale AGN jets

ABSTRACT We analysed the parsec-scale linear polarization properties of 436 active galactic nuclei (AGNs) based on 15 GHz polarimetric Very Long Baseline Array observations. We present polarization and total intensity images averaged over at least five epochs since 1996 January 19 through 2019 August 4. Stacking improves the image sensitivity down to ∼30 μJy beam−1 and effectively fills out the jet cross-section both in total intensity and linear polarization. It delineates the long-term persistent magnetic field configuration and its regularity by restoring spatial distributions of the electric vector position angle (EVPA) and fractional polarization, respectively. On average, about 10 yr of stacking period is needed to reveal the stable and most-complete polarization distribution of a source. We find that the degree of polarization significantly increases down and across the jet towards its edges, typically manifesting U or W-shaped transverse profiles, suggesting a presence of a large-scale helical magnetic field associated with the outflow. In some AGN jets, mainly BL Lacs, we detect quasi-constant fractional polarization profiles across the jet, accompanied by EVPAs that closely follow the outflow. BL Lacs show higher fractional polarization values in their cores and jets than those in quasars up to hectoparsec de-projected scales, while on larger scales, they become comparable. High-synchrotron-peaked BL Lac jets are found to be less polarized than intermediate and low-synchrotron-peaked BL Lacs. The spatial distribution of the EVPAs in BL Lacs tend to align with the local jet direction, while quasars show an excess of orthogonal polarization orientation.

A simple and low-cost directional detection technique for radiation source localization for nuclear security applications

One of the goals in the field of nuclear security is to prevent the misuse and loss of nuclear or other radiological materials. If lost or stolen, radioactive materials could be located and secured using radiation detectors like count rate meters or imaging systems. However, such detectors may not allow for the swift localization of lost sources or may be cost prohibitive in many measurement scenarios. A simple, low-cost, directional radiation detector that is capable of quickly “pointing” towards the nearest radiation source is sought for source search scenarios. Such a detector can be realized using a plastic scintillator couple on each end to photo-multiplier tubes, as shown in this work. The event-by-event position of scintillation in this study is approximated by averaging the amount of light arriving at each of the photomultiplier tubes during coincidence counting. The detector system is then rotated so that the approximated scintillation positions within the detector volume can be determined in other spatial dimensions. A guess vector generated by comparing light ratio skewness produced by the detector in orthogonal orientations points in the direction of a nearby radiation source. An MCNPX-PoliMi model was used to guide the design of such a detector and validate the guess-vector technique. A prototype system using a cube of an EJ-204 plastic scintillator and two photomultiplier tubes was constructed and a correlation between azimuthal source position and detector response was established. For measurements of tens of thousands of counts, the detector prototype generates guess vectors that can identify source position to within 5° uncertainty. The detector prototype can determine the general direction of a nearby source to within 45° uncertainty using 1000 total counts.

Additive manufacturing and performance of bioceramic scaffolds with different hollow strut geometries

Additively manufactured hollow-strut bioceramic scaffolds present a promising strategy towards enhanced performance in patient-tailored bone tissue engineering. The channels in such scaffolds offer pathways for nutrient and cell transport and facilitate effective osseointegration and vascularization. In this study, we report an approach for the slurry based additive manufacturing of modified diopside bioceramics that enables the production of hollow-strut scaffolds with diverse cross-sectional forms, distinguished by different configurations of channel and strut geometries. The prepared scaffolds exhibit levels of porosity and mechanical strength that are well suited for osteoporotic bone repair. Mechanical characterization in orthogonal orientations revealed that a square outer cross-section for hollow struts in woodpile scaffolds gives rise to levels of compressive strength that are higher than those of conventional solid cylindrical strut scaffolds despite a significantly lower density. Finite element analysis confirms that this improved strength arises from lower stress concentration in such geometries. It was shown that hollow struts in bioceramic scaffolds dramatically increase cell attachment and proliferation, potentially promoting new bone tissue formation within the scaffold channel. This work provides an easily controlled method for the extrusion-based 3D printing of hollow strut scaffolds. We show here how the production of hollow struts with controllable geometry can serve to enhance both the functional and mechanical performance of porous structures, with particular relevance for bone tissue engineering scaffolds.

Tri-Cardioid Co-Centered Co-Planar Array—Its Direction-Finding Cramér-Rao Bound and Design Guidelines

Cardioid microphones/hydrophones have a highly directional gain pattern of $[ \alpha + (1 - \alpha) \cos (\beta) ] \cos ^{k}(\beta)$, where $k$ refers to the sensor's directivity order, $\alpha$ denotes the same sensor's cardioidicity index, and $\beta$ represents an impinging signal's incident direction of arrival relative to the cardioid sensor's axis. Three such cardioids organized in orthogonal orientation in three Cartesian spatial dimensions and in spatial colocation as one sensing unit—such a 3-D triad has already attracted much recent attention in the research literature. However, not all three Cartesian coordinates have equal importance to many acoustical applications, which focus alternatively on the azimuthal direction defined on a flat plane but less on the elevation direction normal to that plane. So, this article will instead analyze a 2-D planar configuration of three colocated/cocentered cardioids differently oriented azimuthally apart by $120^\circ$. This aforesaid coplanar triplet conforms to a flat supporting surface more than a Cartesian tridimensionally perpendicular triad can. For such a coplanar triplet composed of cardioids preset at any specific $(k, \alpha)$, the triplet's polar/azimuthal direction-finding Cramér–Rao lower bounds will be analytically derived in closed forms here in this article. Those bounds will be uncovered to exhibit intricate mathematical structures, which will be dissected in detail to yield refined insights, producing simple “actionable” rules-of-thumb to guide the system engineer to choose the appropriate values for $(k, \alpha)$.