Impact of particle size, refractive index, and shape on the determination of the particle scattering coefficient – an optical closure study evaluating different nephelometer angular truncation and illumination corrections

Aerosol particles in the atmosphere interact with solar radiation through scattering and absorption. Accurate aerosol optical properties are needed to reduce the uncertainties of climate predictions. The aerosol optical properties can be obtained via optical modeling based on the measured particle size distribution. This approach requires knowledge or assumptions on the particle refractive index and shape. Meanwhile, integrating nephelometry provides information on the aerosol scattering properties directly. However, their measurements are affected by angular non-idealities, and their data need to be corrected for angular truncation and illumination to provide the particle scattering coefficient. We performed an extensive closure study, including a laboratory and a simulated experiment, aiming to compare different nephelometer angular truncation and illumination corrections (further referred to as "angular corrections"). We focused on coarse mode irregularly shaped aerosols, such as mineral dust, a worldwide abundant aerosol component. The angular correction of irregular particles is found to be only ~2 % higher than the angular correction of volume equivalent spheres. If the angular correction is calculated with Mie theory, the particle size distribution is needed. Our calculations show that if the particle size distribution is retrieved from optical particle spectrometer measurements and the irregular shape effect is not considered, the angular correction can be overestimated by about 5 % and up to 22 %. For mineral dust, the traditional angular correction based on the wavelength dependency of the scattering coefficient seems more accurate. We propose a guideline to establish the most appropriate angular correction depending on the aerosol type and the investigated size range.

An efficient hexagonal image framework using pseudo hexagonal pixel for computer vision applications

Nature-inspired computing has been a real source of motivation for the development of many meta-heuristic algorithms. The biological optic system can be patterned as a cascade of sub-filters from the photoreceptors over the ganglion cells in the fovea to some simple cells in the visual cortex. This spark has inspired many researchers to examine the biological retina in order to learn more about information processing capabilities. The photoreceptor cones and rods in the human fovea resemble hexagon more than a rectangular structure. However, the hexagonal meshes provide higher packing density, consistent neighborhood connectivity, and better angular correction compared to the rectilinear square mesh. In this paper, a novel 2-D interpolation hexagonal lattice conversion algorithm has been proposed to develop an efficient hexagonal mesh framework for computer vision applications. The proposed algorithm comprises effective pseudo-hexagonal structures which guarantee to keep align with our human visual system. It provides the hexagonal simulated images to visually verify without using any hexagonal capture or display device. The simulation results manifest that the proposed algorithm achieves a higher Peak Signal-to-Noise Ratio of 98.45 and offers a high-resolution image with a lesser mean square error of 0.59.

Short lever arm, bipedicular handlebar construct for correction of acute angular kyphosis in spondylodiscitis-induced kyphotic deformity: illustrative case

BACKGROUND Pyogenic spondylodiscitis diminishes spinal structural integrity via disruption of the anterior and middle column, sometimes further compounded by iatrogenic violation of the posterior tension band during initial posterior decompressive surgeries. Although medical management is typically sufficient, refractory infection or progressive deformity may require aggressive debridement and reconstructive arthrodesis. Although anterior debridement plus reconstruction with posterior stabilization is an effective treatment option, existing techniques have limited efficacy for correcting focal deformity, leaving patients at risk for long-term sagittal imbalance, pain, and disability. OBSERVATIONS The authors present a case of chronic lumbar pyogenic spondylodiscitis in a patient in whom initial surgical debridement failed and pronounced angular kyphosis and intractable low back pain developed. A novel bipedicular handlebar construct was used to achieve angular correction of the kyphosis through simultaneous anterior interbody grafting and posterior instrumentation with the patient in the lateral position. LESSONS Leveraging both pedicle screws at the same level to transmit controlled corrective distraction forces through the segment allows for kyphosis correction without relying on long posterior constructs for cantilever reduction. Simultaneous anterior reconstruction with a posterior short lever arm, bipedicular handlebar construct is an effective technique for achieving high angular correction during circumferential reconstructive approaches to postinfectious focal kyphotic deformities.

THEORETICAL GROUNDS FOR ANGULAR CORRECTION OF THE SUPPLY AIR JET FLOW VECTOR IN THE VENTILATION SYSTEMS OF INDUSTRIAL AND AGRICULTURAL FACILITIES

During the heating period, the supply air temperature is lower than that in industrial premises, and the cooled air is denser. Entering a warm room, it tends to move downward. This condition leads to the formation of chilled and stagnant zones. The article presents a theoretical study on the possibility of ensuring the maximum propagation range of a non-isothermal supply air jet by angular correction of the fl ow vector at the outlet of the ventilation unit. Based on the theory of free air distribution, the author analyzed and graphically visualized the fl ow trajectories of the supply air from the combined climate control unit with heat recovery in the production room in the range of outdoor temperatures from +10 to –40°C. Given the time period of outdoor temperatures, fl at sections of a three-dimensional graph were built with a step of 10°C in the range from +10 to –30°C. The author found that the maximum service area of the installation is limited by the propagation range of the supply air jet. The area can be increased by changing the direction of the fl ow vector by an angle ranging between 0 and 34°. The value of the inclination angle of the fl ow vector of the supply air jet is determined by the obtained approximation dependency. Considering the regulation of the fl ow vector, the author used the formula of M.Z. Pechatnikov to determine the propagation range of a limited axisymmetric jet. The studies carried out made it possible to establish the relationship between the propagation range of the supply air jet of the installation and the outside temperature, the inclination angle of the fl ow vector, and the theoretical variation range of the inclination angle of the fl ow vector, ranging between 0 and 34°.

THEORETICAL GROUNDS FOR ANGULAR CORRECTION OF THE SUPPLY AIR JET FLOW VECTOR IN THE VENTILATION SYSTEMS OF INDUSTRIAL AND AGRICULTURAL FACILITIES

During the heating period, the supply air temperature is lower than that in industrial premises, and the cooled air is denser. Entering a warm room, it tends to move downward. This condition leads to the formation of chilled and stagnant zones. The article presents a theoretical study on the possibility of ensuring the maximum propagation range of a non-isothermal supply air jet by angular correction of the fl ow vector at the outlet of the ventilation unit. Based on the theory of free air distribution, the author analyzed and graphically visualized the fl ow trajectories of the supply air from the combined climate control unit with heat recovery in the production room in the range of outdoor temperatures from +10 to –40°C. Given the time period of outdoor temperatures, fl at sections of a three-dimensional graph were built with a step of 10°C in the range from +10 to –30°C. The author found that the maximum service area of the installation is limited by the propagation range of the supply air jet. The area can be increased by changing the direction of the fl ow vector by an angle ranging between 0 and 34°. The value of the inclination angle of the fl ow vector of the supply air jet is determined by the obtained approximation dependency. Considering the regulation of the fl ow vector, the author used the formula of M.Z. Pechatnikov to determine the propagation range of a limited axisymmetric jet. The studies carried out made it possible to establish the relationship between the propagation range of the supply air jet of the installation and the outside temperature, the inclination angle of the fl ow vector, and the theoretical variation range of the inclination angle of the fl ow vector, ranging between 0 and 34°.

A retrospective study of treatment of genu valgum/varum with guided growth: Risk factors for a lower rate of angular correction

The rate of angular correction (ROAC) is very unpredictable and may be affected by various factors in the treatment of genu valgum and varum by means of guided growth. The purpose of this study was to assess the ROAC in cases from our institution and to identify risk factors associated with the occurrence of lower ROAC. We retrospectively reviewed the chart records of 68 patients undergoing guided growth with figure-eight plate for the correction of genu valgum and varum. Based on the data from these patients, the annual increment of physeal growth was calculated and compared with data from the Anderson chart. The associations between patient characteristics and ROAC were evaluated with the use of univariate logistic regression. The mean rate of femoral angular correction was 10.29 degrees/year, while the mean rate of tibial angular correction was 7.92 degrees/year. In a univariate logistic regression analysis, the variables associated with a higher risk of lower ROAC included non-idiopathic coronal deformity of the knee (odds ratio = 13.58, p < 0.001) and body weight at or above the 95th percentile for children (odds ratio = 2.69, p = 0.020). Obesity and non-idiopathic coronal deformity of the knee are risk factors for lower ROAC. It is still uncertain whether severity of deformity, race, and operative procedure have a substantial effect on the rate of correction. Level III evidence.

The effect of temporary hemiepiphysiodesis in the treatment of skeleton immature posttraumatic genu angular deformity: a retrospective study of 27 cases

Background The purpose of this study was to evaluate the effect, rate of angular correction, and complications of temporary hemiepiphysiodesis (TH) in the treatment of skeleton immature posttraumatic genu angular deformity. Methods We retrospectively reviewed the records of 27 patients undergoing temporary hemiepiphysiodesis for the management of posttraumatic genu angular deformity. Based on the data from these patients, the rate of correction, effect of correction, length of the lower limbs, and complications were used as the outcome measures. Results Outcome measurements were obtained from a chart review of medical records that included information about clinical evaluations. Fifteen boys and 12 girls, with an average age of 6.3 years, were included in the study. The average follow-up was 3.8 years (range, 1.9 to 5.9 years) after surgery. Complete correction was obtained in 24 patients, while partial correction was obtained in 3 patients. The mean rate of angular correction was 8.41°/year in distal femur and 15.19°/year in proximal tibia. One patient had recurrence of genu valgum. No leg length discrepancy was found in our patients. Conclusion Temporary hemiepiphysiodesis is a simple, effective, reliable, and reproducible method for the treatment of posttraumatic genu angular deformity, with fewer complications than osteotomy. Nevertheless, it is important to follow the rebound patient closely until skeletal maturity in our future work.

TL 18129 - Surgical treatment of hallux valgus using the percutaneous chevron technique

Objective: To clinically and radiographically observe the outcomes of the surgical treatment of moderate and severe hallux valgus using percutaneous distal chevron osteotomy. Methods: A total of 35 feet (33 patients) with moderate and severe hallux valgus were evaluated using the Couhling classification from June 2016 to January 2018. The mean patient age was 53 years, and the mean postoperative follow-up time was 13 months. All patients who underwent chevron osteotomy were evaluated before and after surgery using the American Orthopedic Foot and Ankle Society (AOFAS) scale. We measured the hallux valgus angle (HVA), the intermetatarsal angle (IMA) and the distal metatarsal articular angle (DMAA) using radiographic studies. Results: The AOFAS score increased by a mean of 54 points. The HVA decreased by a mean of 19°, the IMA by 7° and the DMAA by 11°. The median decrease in the length of the first metatarsal bone was 0.35 cm. Conclusion: Chevron osteotomy using the percutaneous surgical technique made it possible to correct moderate and severe hallux valgus deformities, with excellent angular correction and a significant increase in the AOFAS score.