Wide field-of-hearing metalens for aberration-free sound capture

Metalenses are instruments that manipulate waves and have exhibited remarkable capabilities to date. However, an important hurdle arises due to the severe hampering of the angular response originating from coma and field curvature aberrations, which result in a loss of focusing ability. Herein, we provide a blueprint by introducing the notion of a wide field-of-hearing (FOH) metalens, designed particularly for capturing and focusing sound with decreased aberrations. Employing an aberration-free planar-thin metalens that leverages perfect acoustic symmetry conversion, we experimentally realize a robust wide FOH capability of approximately 140∘ in angular range. Moreover, our metalens features a relatively short focal length, enabling compact implementation by reducing the aperture-to-hearing plane distance. This is beneficial for space-efficient source-tracking sound sensing. Our strategy can be used across various platforms, potentially including energy harvesting, monitoring, imaging, and communication in auditory, ultrasonic, and submerged environments.

Recent advancements of metalenses for functional imaging

Metasurfaces can modulate light with periodically arranged subwavelength scatterers, and they can generate arbitrary wavefronts. Therefore, they can be used to realize various optical components. In particular, metasurfaces can be used to realize lenses, so-called metalenses. In the last decade, metalenses have been actively studied and developed. In this review, we firstly introduce the fundamental principles of metalenses in terms of materials, phase modulation method, and design method. Based on these principles, the functionalities and the applications can consequently be realized. Metalenses have a much larger number of degrees of freedom compared with that of existing refractive or diffractive lenses. Thus, they afford functionalities such as tunability, high numerical aperture, and aberration correction. Metalenses with these functionalities can be applied in various optical systems such as imaging systems and spectrometers. Finally, we discuss the future applications of metalenses.

Scalable manufacturing of high-index atomic layer-polymer hybrid metasurfaces for metaphotonics in the visible

Metalenses are attractive alternatives to conventional bulky refractive lenses owing to their superior light-modulating performance and sub-micrometre-scale thicknesses; however, limitations in existing fabrication techniques, including high cost, low throughput and small patterning area, have hindered their mass production. Here we demonstrate low-cost and high-throughput mass production of large-aperture visible metalenses using deep-ultraviolet argon fluoride immersion lithography and wafer-scale nanoimprint lithography. Once a 12″ master stamp is imprinted, hundreds of centimetre-scale metalenses can be fabricated using a thinly coated high-index film to enhance light confinement, resulting in a substantial increase in conversion efficiency. As a proof of concept, an ultrathin virtual reality device created with the printed metalens demonstrates its potential towards the scalable manufacturing of metaphotonic devices.

Asymmetric Diffraction in Plasmonic Meta-Gratings Using an IT-Shaped Nanoslit Array

Diffraction is a fundamental phenomenon that reveals the wave nature of light. When a plane wave is transmitted or reflected from a grating or other periodic structures, diffracted light waves propagate at several angles that are specified by the period of the given structure. When the optical period is shorter than the wavelength, constructive interference of diffracted light rays from the subwavelength-scale grating forms a uniform plane wave. Many studies have shown that through the appropriate design of meta-atom geometry, metasurfaces can be used to control light properties. However, most semitransparent metasurfaces are designed to perform symmetric operation with regard to diffraction, meaning that light diffraction occurs identically for front- and back-side illumination. We propose a simple single-layer plasmonic metasurface that achieves asymmetric diffraction by optimizing the transmission phase from two types of nanoslits with I- and T-shaped structures. As the proposed structure is designed to have a different effective period for each observation side, it is either diffractive or nondiffractive depending on the direction of observation. The designed structure exhibits a diffraction angle of 54°, which can be further tuned by applying different period conditions. We expect the proposed asymmetric diffraction meta-grating to have great potential for the miniaturized optical diffraction control systems in the infrared band and compact optical diffraction filters for integrated optics.

Recent Progress on Ultrathin Metalenses for Flat Optics

As technology advances, electrical devices such as smartphones have become more and more compact, leading to a demand for the continuous miniaturization of optical components. Metalenses, ultrathin flat optical elements composed of metasurfaces consisting of arrays of subwavelength optical antennas, provide a method of meeting those requirements. Moreover, metalenses have many other distinctive advantages including aberration correction, active tunability, and semi-transparency, compared to their conventional refractive and diffractive counterparts. Therefore, over the last decade, great effort has been focused on developing metalenses to investigate and broaden the capabilities of metalenses for integration into future applications. Here, we discuss recent progress on metalenses including their basic design principles and notable characteristics such as aberration correction, tunability, and multifunctionality.

Multipole decomposition for interactions between structured optical fields and meta-atoms

Interactions between structured optical fields (SOFs) and meta-atoms have been intensively studied, and stimulated by recent advancements on the generation of SOFs and on the synthesis of exotic meta-atoms. Multipole expansion is an efficient and accurate theoretical framework for studying such problems. In this work, explicit expressions of SOFs and their beam-shape coefficients are provided, and their properties are also briefly discussed; the considered SOFs include Laguerre-Gaussian (LG) beams, tightly-focused LG beams, Bessel beams, and cylindrical vector beams. Using the multipole expansion, selective excitations of multipolar resonances of a sphere is discussed. In addition, angular momentum dichroisms of a chiral sphere and an anisotropically chiral meta-atom are calculated to demonstrate selective excitation of multipoles with the desired order, parity, and orientation using engineered SOFs with angular momentum.

Disc degeneration induces a mechano-sensitization of disc afferent nerve fibers that associates with low back pain

OBJECTIVE

We aimed to investigate mechano-sensitivity at the afferent nerve fibers projecting to degenerated intervertebral disc (IVD) and nociceptive behaviour in a rat model of low back pain (LBP).

DESIGN

Animal model with LBP was established by lumbar 4/5 IVD puncture and nucleus pulposus aspiration. In vivo single nerve recordings (n = 121) were introduced to measure discharge frequency at the afferent nerve fiber innervating the IVD during mechanical stimulations (von Frey filament or intradiscal pressure). Nerve growth factor (NGF) expression levels in the IVD (n = 20) were assessed by Western blot. LBP-related behaviour (n = 22) was assessed by measuring changes in rearing, mechanical paw-withdrawal threshold, and dynamic weight bearing in a freely walking rat. Inhibitory effect of morphine on the neuronal excitability (n = 19) and painful behaviour (n = 28) was also assessed.

RESULTS

Compared to those with sham or naïve IVD, animal group with degenerated IVD displayed the sensitized neuronal responses and painful behaviour, with hyperexcitability of the afferent nerve fibers in any range of mechanical stimulations (von Frey filament stimulation; 1, 2, and 26 g; intradiscal pressure, 1,500-3,000 mm Hg), strong upregulation of NGF (200-250 % increase), and LBP-like behaviour such as failure of rearing, front limbs-dependent walking pattern, and hypersensitivity in hind-paws. However, the neuronal hyperexcitability and pain behaviour were attenuated after local (30 μM) or systemic (3 mg kg^-1) morphine administration.

CONCLUSIONS

Our study suggests that enhanced mechano-sensitivity at the afferent nerve fiber innervating degenerated IVD is deeply correlated with LBP development, which supports the hypothesis that hyperexcited responses at the nerve fibers represent a decisive source of LBP.

Compensation of spin-orbit interaction using the geometric phase of distributed nanoslits for polarization-independent plasmonic vortex generation

A metasurface is a planar optical device that controls the phase, amplitude, and polarization of light through subwavelength-scale unit elements, called meta-atom. The tunability of plasmonic vortex lens (PVL) which generates surface plasmon polaritons (SPPs) carrying orbital angular momentum can be improved by using meta-atom. However, conventional PVLs exhibit nonuniform field profiles according to the incident polarization states owing to the spin-orbital interaction (SOI) effect observed during SPP excitation. This paper describes a method of compensating for SOI of PVL by using the geometric phase of distributed nanoslits in a gold film. By designing the orientation angles of slit pairs, the anti-phase of the SOI effect can be generated for compensatory effect. In addition, polarization-independent PVLs are designed by applying a detour phase based on the position of the slit pairs. PVLs for center-, off-center-, and multiple-focus cases are demonstrated and measured via a near-field scanning microscope.

Recurrent Obturator Hernia as a Cause of Nonspecific Abdominal Pain: A Case Report

Many patients visit the emergency department (ED) with abdominal pain. Sometimes, physicians are faced with diagnostic challenges, particularly for older patients. We recently had an elderly female patient who visited the ED several times with non-specific abdominal pain caused by an unusual hernia. One year before, an 81-year-old female visited our ED complaining of abdominal pain radiating to the right inguinal/femoral area. An incarcerated obturator hernia was found on an abdomino-pelvic computed tomography (CT) scan, and she underwent a laparoscopic hernioplasty. However, 1 year later, she revisited complaining of abdominal pain similar to the previous episode. Eventually, the diagnosis of recurrent obturator hernia was made, and a second operation was performed. An obturator hernia may be the cause of non-specific abdominal pain and small bowel obstruction in elderly emaciated females. Recognising the clinical signs and characteristics of this disease is necessary for a prompt diagnosis and treatment.

Tension subcutaneous emphysema during laparoscopic surgery treatment of colon cancer: a case report

Carbon dioxide (CO2) insufflation is now essential for most endoscopic surgeries, such as abdominal, pelvic, and neck endoscopic surgery. It is not uncommon for CO2 leaks to occur unintentionally into subcutaneous tissue, later diffusing into a patient's bloodstream and resulting in hypercarbia. Regardless of the etiology of subcutaneous emphysema, a similar clinical management is required. Herein, we report on a case of tension subcutaneous emphysema and subsequent fatal ventilatory failure due to massive subcutaneous emphysema during laparoscopy. A timely blowhole incision is an effective intervention in an emergent setting like this case, although the patient had endotracheal intubation.

Potential effects of tooth-brushing on human dentin wear following exposure to acidic soft drinks

This study used scanning electron microscopy and atomic force microscopy to examine the short-term potential effects of brushing time and the start-time of tooth-brushing after demineralization on primary dentin wear in vitro. Thirty-six noncarious primary central incisors were assigned to 12 experimental groups. Exposure to cola drinks was used to initiate the demineralization process. Three brushing times (5, 15 and 30 s) and four start-times of brushing (0, 30, 60 and 120 min) after an erosive attack were used for the abrasion process. Tooth-brushing the softened dentin surface led to increases in the open tubular fraction and microstructural changes on the dentin surface. Brushing immediately after exposure to cola resulted in the greatest irreversible dentin loss, whereas brushing 60 or 120 min after pretreatment resulted in the least irreversible dentin loss. However, brushing time had no effect on the irreversible loss of dentin wear. Based on these experimental results, tooth-brushing should be performed at least 60 min after consuming a cola drink to achieve the desired tooth cleaning and avoid the introduction of surface lesions on dentin.

Diagnostic radiopacity and hepatotoxicity following chloroform ingestion: a case report

BACKGROUND

Diagnostic imaging can help in the management of toxicologic emergencies. The authors report on a patient who presented to the emergency department with coma and suppressed respirations after ingestion of an unknown substance.

METHODS

Ingestion of chloroform with radiopaque material in the bowel on abdominal radiograph was documented. The patient was treated with haemoperfusion, activated charcoal, and laxatives to decrease the toxicities.

RESULTS

Hepatotoxicity occurred on post-ingestion day 3 and elevation of liver enzymes reached peak levels on post-ingestion day 5. The patient received N-acetylsystein and supportive care during hospitalisation. The patient improved from hepatic dysfunction and was discharged without complication on post-ingestion day 11.

CONCLUSION

Radiographic studies in toxicology may confirm a diagnosis and assist in therapeutic intervention.

Thoracoscopic plication of diaphragmatic eventration using endostaplers

Unilateral diaphragmatic eventration and paralysis require plication in cases of progressive dyspnea on exertion and recurrent respiratory infection. The patient, a 40-year-old woman, who had complained of worsening dyspnea on exertion and elevation of the left diaphragm on chest radiographs for 4 years, underwent plication by thoracoscopy with knifeless endostaplers. Improvements in pulmonary functions and dyspnea on exertion have been maintained for 14 months.

Fluoroscopy-aided thoracoscopic resection of pulmonary nodule localized with contrast media

BACKGROUND

The pulmonary nodules have become the major indication of video-assisted thoracic surgery (VATS). Recently, several preoperative or intraoperative techniques for identifying small or deeply seated pulmonary nodules have facilitated thoracoscopic resection. We describe the new technique for detecting difficult lesions.

METHODS

Preoperatively, we marked the visceral pleura near the pulmonary nodules with dye, simultaneously injected contrast media (1 water-soluble Optiray [Mallinckrodt Medical Inc, Quebec, Canada], 18 barium sulfate, 11 Lipiodol [Laboratoire Guerbet, Aulnay-sous-Bois, France]) into or around the nodule under computed tomography (CT) guidance. During VATS, we were able to easily and accurately detect and resect all the nodules localized with contrast media, of which the radiopacity was visualized on the portable fluoroscopic monitor.

RESULTS

Between February 1996 and December 1998, we thoracoscopically resected 30 nodules in 28 patients (13 were women; age, 53 +/- 14 years). The resected nodules were 17 +/- 7.6 mm (range; 4 to 32 mm) in size, and 8.9 +/- 8 mm (range, 2 to 34 mm) in depth. The pathologic diagnosis of the nodules was benign in 20 and malignant in 10 (six primary cancers of lung and four metastatic cancers). There were only minor complications related CT localization.

CONCLUSIONS

This new technique can help the surgeons detect and resect the difficult lesions with safety and rapidity by VATS without thoracotomy.

Pulmonary nodules: CT-guided contrast material localization for thoracoscopic resection

Fifteen patients underwent computed tomography (CT)-guided contrast material localization of pulmonary nodules, with barium and indigo carmine stain used in five patients, iodized oil and indigo carmine stain in five, and water-soluble contrast material and indigo carmine stain in five before fluoroscopy-assisted thoracoscopic resection. Contrast material localization was successful in all cases, and the surgeon confirmed accurate localization, CT-guided contrast material localization is simple and useful for thoracoscopic resection.