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Background: Olfactory dysfunction is a cardinal symptom of COVID-19 infection, however, studies assessing long-term olfactory dysfunction are limited and no randomised-controlled trials (RCTs) of early olfactory training have been conducted. Methodology: We conducted a prospective, multi-centre study consisting of baseline psychophysical measurements of smell and taste function. Eligible participants were further recruited into a 12-week RCT of olfactory training versus control (safety information). Patient-reported outcomes were measured using an electronic survey and BSIT at baseline and 12 weeks. An additional 1-year follow-up was open to all participants. Results: 218 individuals with a sudden loss of sense of smell of at least 4-weeks were recruited. Psychophysical smell loss was observed in only 32.1%; 63 participants were recruited into the RCT. The absolute difference in BSIT improvement after 12 weeks was 0.45 higher in the intervention arm. 76 participants completed 1-year follow-up; 10/19 (52.6%) of participants with an abnormal baseline BSIT test scored below the normal threshold at 1-year, and 24/29 (82.8%) had persistent parosmia. Conclusions: Early olfactory training may be helpful, although our findings are inconclusive. Notably, a number of individuals who completed the 1-year assessment had persistent smell loss and parosmia at 1-year. As such, both should be considered important entities of long-Covid and further studies to improve management are highly warranted.

Introduction: In the United States, dentists frequently prescribe hydrocodone. In October 2014, the US Drug Enforcement Administration rescheduled hydrocodone from controlled substance schedule III to II, introducing more restricted prescribing and dispensing regulations, which may have changed dental prescribing of opioids. Objective: The study aim was to evaluate the impact of the hydrocodone rescheduling on dental prescribing of opioids in the United States. Methods: This was a cross-sectional study of opioids prescribed by dentists between October 2012 and October 2016, using the IQVIA Longitudinal Prescription Dataset. Monthly dentist-based opioid prescribing rate (opioid prescription [Rx]/1,000 dentists) and monthly average opioid dosages per prescription (mean morphine milligram equivalent per day [MME/d]) were measured in the 24 mo before and after hydrocodone rescheduling in October 2014 (index or interruption). An interrupted time-series analysis was conducted using segmented ordinary least square regression models, with Newey–West standard errors to handle autocorrelation. Results: Dentists prescribed 50,412,942 opioid prescriptions across the 49 mo. Hydrocodone was the most commonly prescribed opioid pre- and postindex (74.9% and 63.8%, respectively), followed by codeine (13.8% and 21.6%), oxycodone (8.1% and 9.5%), and tramadol (2.9% and 4.8%). At index, hydrocodone prescribing immediately decreased by −834.8 Rx/1,000 dentists (95% confidence interval [CI], −1,040.2 to −629.4), with increased prescribing of codeine (421.9; 95% CI, 369.7–474.0), oxycodone (85.3; 95% CI, 45.4–125.2), and tramadol (111.8; 95% CI, 101.4–122.3). The mean MME increased at index for all opioids except for hydrocodone, and dosages subsequently decreased during the postindex period. Conclusion: Following the rescheduling, dentist prescribing of hydrocodone declined while prescribing of nonhydrocodone opioids increased. Understanding the impact of this regulation informs strategies to ensure appropriate prescribing of opioids for dental pain. Knowledge Transfer Statement: The study findings can be used by policy makers to make informed decisions in developing future risk mitigation strategies aimed to regulate opioid prescribing behaviors. Furthermore, dentist-specific resources and guidelines are needed subsequent to these policies in order to meet the dental population needs.

To enhance the heat transfer of fin-tube surface, two kinds of novel fin-tube surfaces with two rows of tubes in different diameter, arranged in staggered pattern are presented. Along the direction of air flow, the diameter of the first transverse row of tubes is smaller than that of the second. Delta winglet pairs working as longitudinal vortex generators are punched only around the first transverse row of tubes in reduced size, with either “common flow up” or “common flow down” orientation. The performances of two new types of air heat exchangers using the novel fin-tube surfaces (referred as SA and SB) and one traditional plain fin-tube heat exchanger (named BL) acting as baseline in contract are experimentally studied under dry-surface conditions. On the condition of the minimum cross velocity in heat exchanger umax = 4.0 m/s, air-side convective heat transfer coefficients of SA and SB increases by 16.5% and 28.2%, respectively, in comparison with that of BL. The air-side pressure drop decreases less than 10% for SA, and slightly decreases for SB, compared with the baseline heat exchanger. The present results show that one can achieve heat transfer enhancement accompanying with a reduction of pressure loss using the strategies of fin-tube surface, longitudinal vortex generator design and appropriate placement on the fin-tube surfaces.

The ability of an ammonia purifier to reduce oxygen incorporation in AlGaN layers and to improve device performance was investigated. The employment of an ammonia purifier for GaN MOCVD processes showed a reduction of oxygen incorporation in AlGaN layers by a factor of almost 10. “Light output” and “forward voltage” were improved by a factor of 4 times and 10% respectively. Also, no difference in purifier performance was observed between a single use chemisorption-based purifier and a regenerable physisorption-based purifier. It was also demonstrated that the Nanochem ® Regenerable Ammonia Purifier showed no sign of degradation in capacity after 50 regeneration cycles.

Although analyses of in-plane aliasing have been done for conventional computed tomography (CT) images, longitudinal aliasing in spiral CT has not been properly in investigated. The authors propose a mathematical model of the three-dimensional (3-D) sampling scheme in spiral CT and analyze its effects on longitudinal aliasing. They investigated longitudinal aliasing as a function of the helical-interpolation algorithm, pitch, and reconstruction interval using CT simulations and actual phantom scans. The authors' model predicts, and they verified, that for a radially uniform object at the isocenter, the spiral sampling scheme results in spatially varying cancellation of the aliased spectral islands which, in turn, results in spatially varying longitudinal aliasing. The aliasing is minimal at the scanner isocenter, but worsens with distance from it and rapidly becomes significant. The authors' results agree with published results observed at the isocenter of the scanner and further provide new insight into the aliasing conditions at off-isocenter locations with respect to the pitch, interpolation algorithm, and reconstruction interval. The authors conclude that longitudinal aliasing at off-isocenter locations can be significant, and that its magnitude and effects cannot be predicted by measurements made only at the scanner isocenter.

We have used cross-sectional scanning tunneling microscopy (STM) to study interface structure in arsenide/phosphide heterostructures grown by gas-source molecular beam epitaxy. High-resolution images of a sample grown at 550°C and consisting of GaAs interrupted at 200 A intervals with a 40 s P2 flux reveal phosphide interlayers as wide as 30 A and exhibiting lateral variations in structure over nanometer length scales. A similar sample grown at 450°C exhibits narrower interlayers and a lower level of phosphorus incorporation. Data obtained by STM have been corroborated by data from high-resolution X-ray diffraction (HRXRD) and reflection high-energy electron diffraction (RHEED) studies. Together, these studies provide direct information about nanometer-scale grading and lateral nonuniformity of interfaces that can occur under these growth conditions.

P/As exchange behavior on GaAs under a P 2 flux in a gas-source molecular beam epitaxy (GSMBE) system has been studied by reflection high-energy electron diffraction (RHEED), high-resolution double-crystal X-ray rocking curves (DCXRC) and cross-sectional scanning tunneling microscopy (STM). We found that the exposure of GaAs to a P 2 flux results in severe substitution of As atoms by P atoms at the normal temperature for growing GaAs (T s = 570°C). When T s < 500°C, a streaky RHEED pattern can be maintained even during P 2 flux exposure of over 10 min. DCXRC of a 25-period P 2 -exposed GaAs structure grown at 550°C show a set of satellite peaks, indicating formation of a periodic structure. Approximately an average of 0.45 monolayer of phosphorus is incorporated at each interface via As/P exchange. High-resolution cross-sectional STM images reveal non-uniform (both laterally and vertically) interfacial layers of width as large as 10 monolayers. For the sample grown at 450°C, no clear satellite peaks are present. STM images of the sample exhibit much thinner interlayers, consistent with a lower level of phosphorus substitution.

Strain-compensated, highly strained In y Ga 1 − y P/In x Ga 1 − x As/In y Ga 1 − y P quantum wells have been grown by gas-source molecular beam epitaxy (GSMBE) at a wide growth temperature range of 350 to 525°C. From observation of reflection high-energy electron diffraction (RHEED), we find that a low substrate temperature can increase the RHEED critical layer thickness ( l c ), defined as when the RHEED pattern becomes spotty. For In 0.3 Ga 0.7 As, the l c is about 100 A at 500°C and more than 600 A at 350°C. Post-growth annealing can be utilized to increase the quality of strained materials grown at low temperature. Strain compensation is also shown to improve thermal stability against annealing.

We have shown that strain compensation is effective in increasing the critical layer thickness or the critical number of periods in a multiple quantum well (MQW) structure and in improving thermal stability. Compared with a strain-uncompensated InAs 0.4 P 0.6 InP MQW (1.3% strain) on InP substrates, strain-compensated InAs 0.4 P 0.6 Ga y In 1 − y P MQW in a p-i-n structure exhibits superior structural and optical properties, especially electroabsorption characteristics that is suitable for modulator applications at 1.3 μm. Strain-compensated In 0.3 Ga 0.7 As Ga y In 1 − y P MQWs on GaAs substrates exhibit better photoluminescence properties and are shown to be more thermally stable.

We have used cross‐sectional scanning tunneling microscopy to study interface structure in arsenide/phosphide heterostructures grown by gas‐source molecular beam epitaxy. High‐resolution images of a sample grown at 550 °C by interrupting the growth of GaAs at 200 A intervals with a 40 s P2 flux reveal phosphide interlayers of widths as large as 30 A with lateral variations in structure over