Acoustic sorting of airborne particles by a phononic crystal waveguide

A two-dimensional phononic crystal linear defect waveguide is utilized for size-based sorting of millimeter-sized solid particles in the air through acoustic radiation force. The waveguide channels ultrasonic waves at 20 kHz, as calculated through Finite-Element Method simulations. Spherical solid particles released from rest at the top of the vertically aligned waveguide experience the combined effect of the acoustic radiation, gravity, and drag forces. When the particles are released from the symmetry plane of the waveguide, they follow straight paths where the ones with radii smaller than a threshold value are trapped at the waveguide nodal planes, whereas larger particles are let pass through. This requires input sound pressure levels between 173 dB and 177 dB. Moreover, such particles can also be differentiated with respect to density. Alternatively, the release of particles with a slight offset from the symmetry center induces unbalanced acoustic radiation potential, and thus uneven radiation force, resulting in the initiation of horizontal displacement whose extent depends on particle radius. Thus, both simulation results and experimental findings suggest that this scheme can be employed in size-based particle separation. Sorting of spherical glass particles with 0.5 mm and 1.0 mm radii are experimentally demonstrated for low ultrasonic transducer acoustic power output up to 90 W. The proposed approach can be utilized in applications where contact-free separation of airborne particles is required.

Peri-implant bone defects: A 1-year follow-up comparative study of use of hyaluronic acid and xenografts

Objective

The aim of this study was to compare the efficacy of hyaluronic acid (HA) and xenografts on the repair of peri-implant dehiscence-type bone defects occur during implant placement.

Patients and Methods

Forty-two dehiscence Class I type defects located on the buccal surface of the implants were included in this study. Defects were divided into two main groups as small sized (height of <3 mm) and medium sized (height between 3 and 5 mm). Both of the main groups were further divided into two subgroups as HA plus xenograft plus collagen membrane (HAXC) or xenograft plus collagen membrane (XC) applied groups. After grafting, repair of defect site was evaluated with the help of the cross-sectional images on cone-beam computed tomography at 6^th and 12^th months.

Results

In both main groups, vertical bone height (VBH) was higher in defects repaired with HAXC (2.65 ± 1.12 mm) than in the XC (2.45 ± 1.10 mm) groups at the 6^th month. However, the difference between two subgroups was not statistically significant (P > 0.05). Reduction in VBH was observed up to 6-12 months after prosthetic loading in all defect sites. This reduction was found statistically significant in medium-sized defects that grafted with XC (P < 0.05, paired t-test). However, in other subgroups, the difference between measurements at 6^th and 12^th months was not statistically significant (P > 0.05).

Conclusions

According to the data obtained from this study, it can be concluded that HA did not have a significant positive effect on the repair of defects around dental implants.

An In-vitro study on thermal changes during implant drilling with different irrigation volumes

Objective

Irrigation with saline is one of the essential methods for reducing the heat generated during dental implant osteotomy. High irrigation volume impairs visibility of the surgical field, thus complicates the surgery. In this study, we aimed to determine the optimal irrigation volume for heat reduction during dental implant drilling.

Materials and Methods

Thirty-two implant osteotomies were prepared on four fresh cow ribs. Heat generated during the final implant drilling was measured both with infrared thermography and thermocouple method. Initial and maximum temperatures were measured at four different irrigation volumes; 32, 44, 56, and 68 ml/min.

Results

Both measurement methods showed that the amount of temperature rise is associated with the irrigation volume during implant drilling. There is no further decrease in temperature rise above irrigation volume of 56 ml/min.

Conclusion

Saline irrigation with 56 ml/min provides sufficient heat reduction during dental implant drilling and higher irrigation volumes are not necessary.

Acoustic Tamm states of three-dimensional solid-fluid phononic crystals

In this work, the existence and propagation of acoustic Tamm states at the interface of air and a face-centered cubic solid-fluid phononic crystal composed of spherical air voids interconnected by cylindrical air channels are demonstrated. Supercell band structure computations via the finite element method reveal surface bands for Tamm states on (100), (110), and (111) surfaces of the phononic crystal. The states decay sharply into the phononic crystal so that only a two-row slab is sufficient to guide them over the respective surfaces without leakage, as confirmed by finite element simulations. In addition, surface wave propagation along the [10] direction of the (100) surface is experimentally demonstrated. Ability to confine the Tamm states in all three dimensions is a key aspect in designing few-layer-thick acoustic circuits. Low material filling fraction of the phononic crystal could be leveraged to realize lightweight all-acoustic systems where either bulk or surface states can be incorporated.

Acoustophoretic separation of airborne millimeter-size particles by a Fresnel lens

We numerically demonstrate acoustophoretic separation of spherical solid particles in air by means of an acoustic Fresnel lens. Beside gravitational and drag forces, freely-falling millimeter-size particles experience large acoustic radiation forces around the focus of the lens, where interplay of forces lead to differentiation of particle trajectories with respect to either size or material properties. Due to the strong acoustic field at the focus, radiation force can divert particles with source intensities significantly smaller than those required for acoustic levitation in a standing field. When the lens is designed to have a focal length of 100 mm at 25 kHz, finite-element method simulations reveal a sharp focus with a full-width at half-maximum of 0.5 wavelenghts and a field enhancement of 18 dB. Through numerical calculation of forces and simulation of particle trajectories, we demonstrate size-based separation of acrylic particles at a source sound pressure level of 153 dB such that particles with diameters larger than 0.5 mm are admitted into the central hole, whereas smaller particles are rejected. Besides, efficient separation of particles with similar acoustic properties such as polyethylene, polystyrene and acrylic particles of the same size is also demonstrated.

Phononic crystal surface mode coupling and its use in acoustic Doppler velocimetry

It is numerically shown that surface modes of two-dimensional phononic crystals, which are Bloch modes bound to the interface between the phononic crystal and the surrounding host, can couple back and forth between the surfaces in a length scale determined by the separation of two surfaces and frequency. Supercell band structure computations through the finite-element method reveal that the surface band of an isolated surface splits into two bands which support either symmetric or antisymmetric hybrid modes. When the surface separation is 3.5 times the lattice constant, a coupling length varying between 30 and 48 periods can be obtained which first increases linearly with frequency and, then, decreases rapidly. In the linear regime, variation of coupling length can be used as a means of measuring speeds of objects on the order of 0.1m/s by incorporating the Doppler shift. Speed sensitivity can be improved by increasing surface separation at the cost of larger device sizes.

Sharp bends of phononic crystal surface modes

Sharp bending of surface waves at the interface of a two-dimensional phononic crystal (PnC) of steel cylinders in air and the method of using a diagonally offset cylindrical scatterer are numerically demonstrated by finite-element method simulations. The radii of the diagonally offset scatterer and the cylinder at the PnC corner, along with the distance between them, are treated as optimization parameters in the genetic algorithm optimization of sharp bends. Surface wave transmittance of at most 5% for the unmodified sharp bend is significantly enhanced to approximately 75% as a result of optimization. A series of transmittance peaks whose maxima increase exponentially, as their widths reduce, with increasing frequency is observed for the optimized sharp bend. The transmittance peaks appear at frequencies corresponding to integer plus half-beat periods, depending on the finite surface length. The optimal parameters are such that the cylinder radius at the PnC corner is not significantly modified, whereas a diagonally offset scatterer having a diameter of almost two periods and a shortest distance of about 0.7 periods between them is required for the strongest transmittance peak. Utilization of PnC surface sharp bends as acoustic ring resonators is demonstrated.

Demodex folliculorum in polycystic ovary syndrome patients

OBJECTIVE

In this study, we aimed to investigate frequency of Demodex (D.) folliculorum infestation in Polycystic Ovary Syndrome patients.

PATIENTS AND METHODS

The study population consisted of 30 PCOS patients and 30 matched healthy control subjects admitted to the Hospital of Mustafa Kemal University, Gynecology and Obstetrics Clinic between March 2013 and January 2014. The demographic characteristics of the patients were recorded. Samples from the face region of the subjects were taken by standard method of superficial skin biopsy and evaluated by microscopy. Presence of five or more D. species in a cm2 was considered as positive.

RESULTS

There were no significant differences in age, body mass index, diabetes mellitus incidence between PCOS patients and the control group. However, D. folliculorum infestation was found to increased in PCOS patients (n = 9; 30%) when compared to the control group (n = 2; 6, 7%) (p: 0.04).

CONCLUSIONS

Our study results revealed that Demodex folliculorum appearance increased in PCOS patients.

Acoustic waveguiding by pliable conduits with axial cross sections as linear waveguides in two-dimensional sonic crystals

Pliable conduits composed of periodically arranged concentric aluminum tori in air, with their axial cross sections acting as linear waveguides in two-dimensional sonic crystals, are numerically shown to guide acoustic waves in three dimensions in a flexible manner. Waveguide band structures are obtained by exploiting axial symmetry in a super-cell approach through two-dimensional finite-element simulations under the periodic boundary conditions. One isolated band having a bandwidth of 19.66% or 10.10% is observed for each guide, whose cross section is either in square or triangular geometry, respectively. Corresponding mode profiles indicate efficient guiding, as the acoustic energy is mainly concentrated in the hollow-core region of the guides. Transmittance spectra calculated through finite-element simulations are in agreement with the computed guiding bands. Transmittance along the waveguides with square and triangular axial cross sections around mid-band frequencies of their guiding bands varies slightly from -6.05 and -6.65 dB to -5.98 and -8.86 dB, respectively, as the guide length is increased from 10 to 200 periods. Efficient guiding across the smooth bends over circular arcs up to 90 deg is also demonstrated through three-dimensional finite-element method simulations.

Refraction-based photonic crystal diode

A system composed of air holes in a dielectric host to form two square photonic crystals, with the same orientation and lattice constant but different scatterer radii, making an interface along their body diagonals, is numerically demonstrated to facilitate unidirectional light transmission. Band structure computations are carried out via the plane wave expansion method, whereas finite-difference time-domain simulations are carried out to investigate the transient behavior. Unidirectional light transmission is achieved over two adjacent stop bands along the ΓX direction, which are circumvented in the forward direction by scaling down the wave vector and rotating the surface normal. Contrast ratios as high as 0.9 are attained within the lower stop band.

Pressure field of rectangular transducers at finite amplitude in three dimensions

In this study, the nonlinear pressure fields of various sized rectangular transducers are modeled in three dimensions. The model was based on Aanonsen's model, which has earlier been presented for circular sources. The nonlinear wave propagation at finite amplitude is presented for square and rectangular type sources up to three harmonics. Numerical results are also tested using available experimental measurements on the acoustic axis. Good agreement is shown with the experiment for both square and rectangular cases.