Nano-structure fabrication of GaAs using AFM tip-induced local oxidation method: different doping types and plane orientations

In this study, we have fabricated nano-scaled oxide structures on GaAs substrates that are doped in different conductivity types of p- and n-types and plane orientations of GaAs(100) and GaAs(711), respectively, using an atomic force microscopy (AFM) tip-induced local oxidation method. The AFM-induced GaAs oxide patterns were obtained by varying applied bias from approximately 5 V to approximately 15 V and the tip loading forces from 60 to 180 nN. During the local oxidation, the humidity and the tip scan speed are fixed to approximately 45% and approximately 6.3 μm/s, respectively. The local oxidation rate is further improved in p-type GaAs compared to n-type GaAs substrates whereas the rate is enhanced in GaAs(100) compared to and GaAs(711), respectively, under the identical conditions. In addition, the oxide formation mechanisms in different doping types and plane orientations were investigated and compared with two-dimensional simulation results

Biofilm formation and virulence expression by Streptococcus mutans are altered when grown in dual-species model

<p>Abstract</p> <p>Background</p> <p>Microbial cell-cell interactions in the oral flora are believed to play an integral role in the development of dental plaque and ultimately, its pathogenicity. The effects of other species of oral bacteria on biofilm formation and virulence gene expression by <it>Streptococcus mutans</it>, the primary etiologic agent of dental caries, were evaluated using a dual-species biofilm model and RealTime-PCR analysis.</p> <p>Results</p> <p>As compared to mono-species biofilms, biofilm formation by <it>S. mutans </it>was significantly decreased when grown with <it>Streptococcus sanguinis</it>, but was modestly increased when co-cultivated with <it>Lactobacillus casei</it>. Co-cultivation with <it>S. mutans </it>significantly enhanced biofilm formation by <it>Streptococcus oralis </it>and <it>L. casei</it>, as compared to the respective mono-species biofilms. RealTime-PCR analysis showed that expression of <it>spaP </it>(for multi-functional adhesin SpaP, a surface-associated protein that <it>S. mutans </it>uses to bind to the tooth surface in the absence of sucrose), <it>gtfB </it>(for glucosyltransferase B that synthesizes α1,6-linked glucan polymers from sucrose and starch carbohydrates) and <it>gbpB </it>(for surface-associated protein GbpB, which binds to the glucan polymers) was decreased significantly when <it>S. mutans </it>were co-cultivated with <it>L. casei</it>. Similar results were also found with expression of <it>spaP </it>and <it>gbpB</it>, but not <it>gtfB</it>, when <it>S. mutans </it>was grown in biofilms with <it>S. oralis</it>. Compared to mono-species biofilms, the expression of <it>luxS </it>in <it>S. mutans </it>co-cultivated with <it>S. oralis </it>or <it>L. casei </it>was also significantly decreased. No significant differences were observed in expression of the selected genes when <it>S. mutans </it>was co-cultivated with <it>S. sanguinis</it>.</p> <p>Conclusions</p> <p>These results suggest that the presence of specific oral bacteria differentially affects biofilm formation and virulence gene expression by <it>S. mutans</it>.</p

Long-term outcomes after revascularization for advanced popliteal artery entrapment syndrome with segmental arterial occlusion

ObjectivesThere are few long-term follow-up studies about the result of revascularization surgery for the treatment of popliteal artery entrapment syndrome (PAES). We performed this retrospective study to analyze the long-term result of revascularization surgery in patients with advanced PAES during the last 16 years.MethodsTwenty-two limbs in 18 consecutive patients with PAES were treated surgically at Seoul National University Hospital between January 1994 and December 2009. The preoperative diagnosis of PAES was made by duplex ultrasonography, three-dimensional computed tomography angiography, magnetic resonance imaging, or conventional angiography. The method of surgical approach was determined by the extent of arterial occlusion in preoperative images.ResultsThe mean age was 31 years old and the majority of patients were men (94%). The chief complaints were claudication in 18 limbs, ischemic rest pain in three limbs, and toe necrosis in one limb. All 22 limbs underwent revascularization for advanced PAES with segmental arterial occlusion. Fourteen limbs underwent musculotendinous section and popliteo-popliteal interposition graft (13 posterior approaches, one medial approach), five femoropopliteal (below-knee) bypasses, one femoro-posterior tibial bypass, and two popliteo-posterior tibial bypasses. All revascularization surgeries were performed with reversed saphenous veins. The overall primary graft patency rates at 1, 3, and 5 years were 80.9%, 74.6%, and 74.6%, respectively. Comparing 5-year graft patency according to the extent of arterial occlusion, patients with occlusion confined to the popliteal artery (n = 14) showed a better patency rate than patients with occlusion extended beyond the popliteal artery (n = 8) with no statistical significance (83.6% vs 53.6%; P = .053). Comparing 5-year graft patency according to the inflow artery, superficial femoral artery inflow (n = 6) showed a worse patency rate than popliteal artery inflow (n = 16) (30.0% vs 85.9%; P = .015).ConclusionIn advanced popliteal entrapment syndrome, longer bypass with superficial femoral artery inflow showed poor long-term graft patency rate. The graft patency rate was excellent in patients whose arterial occlusion was confined to the popliteal artery and treated by popliteal interposition graft with reversed saphenous vein. With these data, we suggest that longer bypass extending beyond the popliteal artery might only be indicated in patients with critical limb ischemia when the extent of disease does not allow short interposition graft

Metal work-function-dependent barrier height of Ni contacts with metal-embedded nanoparticles to 4H-SiC

Metal, typically gold [Au], nanoparticles [NPs] embedded in a capping metal contact layer onto silicon carbide [SiC] are considered to have practical applications in changing the barrier height of the original contacts. Here, we demonstrate the use of silver [Ag] NPs to effectively lower the barrier height of the electrical contacts to 4H-SiC. It has been shown that the barrier height of the fabricated SiC diode structures (Ni with embedded Ag-NPs) has significantly reduced by 0.11 eV and 0.18 eV with respect to the samples with Au-NPs and the reference samples, respectively. The experimental results have also been compared with both an analytic model based on Tung's theory and physics-based two-dimensional numerical simulations

Retrieval of NO2 Column Amounts from Ground-Based Hyperspectral Imaging Sensor Measurements

Total column amounts of NO2 (TCN) were estimated from ground-based hyperspectral imaging sensor (HIS) measurements in a polluted urban area (Seoul, Korea) by applying the radiance ratio fitting method with five wavelength pairs from 400 to 460 nm. We quantified the uncertainty of the retrieved TCN based on several factors. The estimated TCN uncertainty was up to 0.09 Dobson unit (DU), equivalent to 2.687 ?? 1020 molecules m???2) given a 1?? error for the observation geometries, including the solar zenith angle, viewing zenith angle, and relative azimuth angle. About 0.1 DU (6.8%) was estimated for an aerosol optical depth (AOD) uncertainty of 0.01. In addition, the uncertainty due to the NO2 vertical profile was 14% to 22%. Compared with the co-located Pandora spectrophotometer measurements, the HIS captured the temporal variation of the TCN during the intensive observation period. The correlation between the TCN from the HIS and Pandora also showed good agreement, with a slight positive bias (bias: 0.6 DU, root mean square error: 0.7 DU)

Characterizing Natural User Interface with Wearable Smart Watches

Background - The emergence of new interaction paradigms makes the use of technology inrealizing the users??? natural ways of exploring the real world the ultimate goal of designers today.Research on interactive and immersive technologies for user interface design is still a challenging chore for engineers and scientists when it comes to designing natural interaction for wearable smart devices. To address the challenge, our study aims to develop guidelines for design practitioners in designing wearable smart watches that could offer natural user experiences. Methods - To better understand natural user experiences with smart watches, an extensive literature review was conducted. A quantitative survey with 80 participants was conducted, of which the focus was on the expected functions of smart watches. Based on the survey results, we selected eight participants in terms of technology familiarity. To achieve the objectives of our research, three studies were conducted: a design workshop (Study 1), a cultural probe (Study 2), and a focus group interview (Study 3). The design workshop was created to figure out the needs and wishes people have forsmart watches. In the cultural probe, the focus was on figuring out natural interactions with smart watches. Finally, the focus group interview aimed to gain more insights from the results of the cultural probe in terms of natural user interaction with particular functions. Results - To address the needs and wishes of the users toward wearable smartwatches, we made a subdivision into three categories, such as functions, input measures, and notification (feedback) methods. According to the results, participants wanted weather notification, health monitoring, and identification as expected functions. Regarding the methodof input, voice command and touch screen were preferred. In order to get feedback, most of the participantswanted vibrations, particularly as a reaction tocompleting the commands or inputs. There was also a suggestion to customize their smart watch. For example, users can select the functions and build their own command system, and even choose the notificationmethods. Considering natural user interface with respect to functions (weather, answering a call, navigation, health monitoring, taking a picture and messaging), specific natural user interfaces were mentioned for particular functions. Conclusions - Throughout the study, people???s needs and wishes and their perceptions about natural interaction were identified and the characteristics of natural user interfacesweredetermined. Based on the results, tenperceptions were specifically defined to provide a better understanding of smart watches in terms of natural interaction: user affinity of form, awareness by familiarity, reality correspondence, behavioral extension, purpose orientation, easiness of performance, timeliness, routine acceptance, generality, and rule of thumb. In addition to that, natural user interfaces were categorized into five groups: user familiarity, realistic interaction, accomplishment assistance, contextual appropriateness, and social awareness. In this study,we tried to identify what constitutes anatural interaction and how it should be created. The limitations and further study are discussed at the end.ope

Elevated CO2 may alter pheromonal communication in Helicoverpa armigera (Lepidoptera: Noctuidae)

Carbon dioxide (CO2) as a greenhouse gas has been increasing in recent decades. Because an elevated atmospheric CO2 influences insect physiology and behaviour, we hypothesize that pheromone-mediated communication in the moth is affected by an increased CO2 level. We test the behavioural responses of male Helicoverpa armigera to sex pheromone in a wind tunnel, demonstrating a significant reduction of approaching behaviour to the odour source at a high CO2 level (1000ppm). Electroantennogram (EAG) responses of male to the pheromone component are also significantly suppressed in high CO2 environments (600 and 1000ppm), indicating that a high CO2 level inhibits both behavioural and electrophysiological responses of male to the sex pheromone. Interestingly, the EAG response of the whole head preparation of males is influenced more by the elevated CO2 level than that of the antenna-cut preparation. A sequential increase of CO2 levels from an ambient CO2 level also decreases the EAG response of the whole head but not of the labial palp-removed head, implying a potential mediation of labial palp in the head where the CO2 receptor is located. By contrast, sex pheromone production in females reared under or shifted to an elevated CO2 condition is increased, and the putative underlying mechanism for this is discussed. The present study provides an insight into the adaptive strategy of moth pheromone communication in a changing environment

mRNA vaccine effectiveness against SARS-CoV-2 B.1.617.2 (Delta) and B.1.1.529 (Omicron) variant transmission from home care cases to household contacts in South Korea

Objectives Household contacts of confirmed cases of coronavirus disease 2019 (COVID-19) are exposed to a high risk of viral transmission, and secondary incidence is an important indicator of community transmission. This study analyzed the secondary attack rate and mRNA vaccine effectiveness against transmission (VET) for index cases (patients treated at home) confirmed to be infected with the Delta and Omicron variants. Methods The subjects of the study were 4,450 index cases and 10,382 household contacts. Logistic regression analysis was performed to compare the secondary attack rate by vaccination status, and adjusted relative risk and 95% confidence intervals were identified. Results The secondary attack rate of the Delta variant was 27.3%, while the secondary attack rate of the Omicron variant was 29.8%. For the Delta variant, groups with less than 90 days and more than 90 days after 2 doses of mRNA vaccination both showed a VET of 37%. For the Omicron variant, a 64% VET was found among those with less than 90 days after 2 doses of mRNA vaccination. Conclusion This study provides useful data on the secondary attack rate and VET of mRNA vaccines for household contacts of COVID-19 cases in South Korea