Uniform large-area surface patterning achieved by metal dewetting for the top-down fabrication of GaN nanowire ensembles.

The dewetting of thin Pt films on different surfaces is investigated as a means to provide the patterning for the top-down fabrication of GaN nanowire ensembles. The transformation from a thin film to an ensemble of nanoislands upon annealing proceeds in good agreement with the void growth model. With increasing annealing duration, the size and shape uniformity of the nanoislands improves. This improvement speeds up for higher annealing temperature. After an optimum annealing duration, the size uniformity deteriorates due to the coalescence of neighboring islands. By changing the Pt film thickness, the nanoisland diameter and density can be quantitatively controlled in a way predicted by a simple thermodynamic model. We demonstrate the uniformity of the nanoisland ensembles for an area larger than 1 cm2. GaN nanowires are fabricated by a sequence of dry and wet etching steps, and these nanowires inherit the diameters and density of the Pt nanoisland ensemble used as a mask. Our study achieves advancements in size uniformity and range of obtainable diameters compared to previous works. This simple, economical, and scalable approach to the top-down fabrication of nanowires is useful for applications requiring large and uniform nanowire ensembles with controllable dimensions.

ScN/GaN(11Ì 00): A New Platform for the Epitaxy of Twin-Free Metal-Semiconductor Heterostructures.

We study the molecular beam epitaxy of rock-salt ScN on the wurtzite GaN(11̅00) surface. To this end, ScN is grown on freestanding GaN(11̅00) substrates and self-assembled GaN nanowires exhibiting (11̅00) sidewalls. On both substrates, ScN crystallizes twin-free thanks to a specific epitaxial relationship, namely ScN(110)[001]∥GaN(11̅00)[0001], providing a congruent, low-symmetry interface. The 13.1% uniaxial lattice mismatch occurring in this orientation mostly relaxes within the first few monolayers of growth by forming a near-coincidence site lattice, where 7 GaN planes coincide with 8 ScN planes, leaving the ScN surface nearly free of extended defects. Overgrowth of the ScN with GaN leads to a kinetic stabilization of the zinc blende phase, that rapidly develops wurtzite inclusions nucleating on {111} nanofacets, commonly observed during zinc blende GaN growth. Our ScN/GaN(11̅00) platform opens a new route for the epitaxy of twin-free metal-semiconductor heterostructures including closely lattice-matched GaN, ScN, HfN, and ZrN compounds.

Dermatology teaching for undergraduate medical students in clinical routine - a structured four-week curriculum.

BACKGROUND: Dermatology teaching is fundamental for the promotion of young colleagues in our specialty. However, traditional teaching methods are being scrutinized by students of the 'Generation Y and Z', which can pose new challenges for teaching institutions. We therefore aimed to assess the motivational impact and reception of a newly created four-week curriculum containing modernized teaching methods integrated into clinical routine. METHODS: In this single-center study, 67 medical students completed this curriculum composed of weekly learning objectives including knowledge of morphological terms, 10 common dermatoses, communication and presentation skills. The participants provided information on their level of interest in dermatology each week as well as positive and negative aspects of the curriculum. RESULTS: During the curriculum a significant median increase in interest in dermatology was reported with no differences between the genders. Low initial interest could be improved, high initial interest maintained. Participants with an interest in scientific work (20.9%) were more motivated during the curriculum. The variety, quality of teaching and structure were the main aspects rated positively. Suggestions for improvement included the need for more teaching by senior doctors, transfer of responsibility, and a working environment updated to the latest technology standards. CONCLUSION: The presented curriculum was well received by the participants and allowed to better define learning preferences of new generations which can be helpful to modernize traditional teaching methods. Interest in scientific work could be a factor to identify students with a particularly strong interest in dermatology.

Growth mechanisms in molecular beam epitaxy for GaN-(In,Ga)N core-shell nanowires emitting in the green spectral range.

Using molecular beam epitaxy, we demonstrate the growth of (In,Ga)N shells emitting in the green spectral range around very thin (35 nm diameter) GaN core nanowires. These GaN nanowires are obtained by self-assembled growth on TiN. We present a qualitative shell growth model accounting for both the three-dimensional nature of the nanostructures as well as the directionality of the atomic fluxes. This model allows us, on the one hand, to optimise the conditions for high and homogeneous In incorporation and, on the other hand, to explain the influence of changes in the growth conditions on the sample morphology and In content. Specifically, the impact of the V/III and In/Ga flux ratios, the rotation speed and the rotation direction are investigated. Notably, with In acting as surfactant, the ternary (In,Ga)N shells are much more homogeneous in thickness along the nanowire length than their binary GaN counterparts.

X-ray scattering study of GaN nanowires grown on Ti/Al2O3 by molecular beam epitaxy.

GaN nanowires (NWs) grown by molecular beam epitaxy on Ti films sputtered on Al2O3 are studied by X-ray diffraction (XRD) and grazing-incidence small-angle X-ray scattering (GISAXS). XRD, performed both in symmetric Bragg reflection mode and at grazing incidence, reveals Ti, TiN, Ti3O, Ti3Al and Ga2O3 crystallites with in-plane and out-of-plane lattice parameters intermediate between those of Al2O3 and GaN. These topotaxial crystallites in the Ti film, formed as a result of interfacial reactions and N exposure, possess little misorientation with respect to Al2O3. As a result, GaN NWs grow on the top TiN layer, possessing a high degree of epitaxial orientation with respect to the substrate. The measured GISAXS intensity distributions are modelled by the Monte Carlo method, taking into account the orientational distributions of NWs, the variety of their cross-sectional shapes and sizes, and the roughness of their side facets. The cross-sectional size distributions of the NWs and the relative fractions of the {1100} and {1120} side facets are determined.

Colchicine - Renaissance of an "ancient" drug.

Colchicine, which was already used by the ancient Egyptians, has recently experienced a renaissance in various medical disciplines, including dermatology. However, due to the potentially significant side effects of systemic use, many clinicians are cautious in their use of colchicine. This review provides a practical overview of the data on the established and emerging use of systemic and topical colchicine in dermatologic diseases.

Cross-sectional shape evolution of GaN nanowires during molecular beam epitaxy growth on Si(111).

We study the cross-sectional shape of GaN nanowires (NWs) by transmission electron microscopy. The shape is examined at different heights of long NWs, as well as at the same height for NWs of different lengths. Two distinct trends in the evolution of the cross-sectional shape along the NW length are observed. At the top, merging NWs develop common {11̄00} side facets. At the bottom, the NWs acquire roundish shapes. This observation is explained by the entirely different NW environments at the top and the bottom of the NWs. At the top, NWs are exposed to the Ga and N atomic fluxes giving rise to axial growth, resulting in the equilibrium growth shape with zero growth rate at the {11̄00} facets. At the bottom, NWs are shadowed from the impinging fluxes and are only annealed, allowing them to eventually approach the equilibrium crystal shape. The study of identical samples by grazing incidence small-angle X-ray scattering independently confirms these trends in the shape evolution of the sidewall facets.

Association between allergic sensitization and intestinal parasite infection in schoolchildren in Gqeberha, South Africa.

BACKGROUND: Inconsistent data exist regarding the influence of parasitic infection on the prevalence of allergic sensitization and disorders. OBJECTIVE: To investigate the impact of geohelminth and protozoan infections on sensitization patterns and allergic symptoms of children living in low-income communities in Gqeberha, South Africa. METHODS: In a cross-sectional study, 587 schoolchildren aged 8-12 years were recruited in June 2016 and screened for reactivity to common allergens by skin prick tests (SPTs) and for parasitic infections by stool examination. Additionally, questionnaires were completed to record allergic symptoms the children may have experienced. RESULTS: Positive SPTs were found in 237/587 children (40.4%), and about one-third of whom were polysensitized. Sensitizations were most frequently detected against the house dust mites (HDM) Dermatophagoides spp. (31.9%) and Blomia tropicalis (21.0%). Infections with geohelminths (Ascaris lumbricoides, Trichuris trichiura) were found in 26.8% and protozoan infections (Giardia intestinalis, Cryptosporidia spp.) in 13.9% of study participants. Mixed logistic regression analyses revealed negative associations between parasite infection and sensitization to Blomia tropicalis (OR: 0.54, 95% CI 0.33-0.89) and to Dermatophagoides spp. (OR 0.65, 95% CI 0.43-0.96), and between protozoan infection and allergic sensitization to any aeroallergen, although these associations were not significant when adjusted for false discovery. Geohelminth infection and intensity of geohelminth infection were both associated with reduced risk of polysensitization (OR 0.41, 95% CI 0.21-0.86), and this association remained significant with adjustment for false discovery. Reported respiratory symptoms were associated with HDM sensitization (ORs from 1.54 to 2.48), but not with parasite infection. CONCLUSIONS AND CLINICAL RELEVANCE: Our data suggest that geohelminth infection and high geohelminth infection intensity are associated with a reduced risk of polysensitization.

Drastic Effect of Sequential Deposition Resulting from Flux Directionality on the Luminescence Efficiency of Nanowire Shells.

Core-shell nanowire heterostructures form the basis for many innovative devices. When compound nanowire shells are grown by directional deposition techniques, the azimuthal position of the sources for the different constituents in the growth reactor, substrate rotation, and nanowire self-shadowing inevitably lead to sequential deposition. Here, we uncover for In0.15Ga0.85As/GaAs shell quantum wells grown by molecular beam epitaxy a drastic impact of this sequentiality on the luminescence efficiency. The photoluminescence intensity of shell quantum wells grown with a flux sequence corresponding to migration enhanced epitaxy, that is, when As and the group-III metals essentially do not impinge at the same time, is more than 2 orders of magnitude higher than for shell quantum wells prepared with substantially overlapping fluxes. Transmission electron microscopy does not reveal any extended defects explaining this difference. Our analysis of photoluminescence transients shows that co-deposition has two detrimental microscopic effects. First, a higher density of electrically active point defects leads to internal electric fields reducing the electron-hole wave function overlap. Second, more point defects form that act as nonradiative recombination centers. Our study demonstrates that the source arrangement of the growth reactor, which is of mere technical relevance for planar structures, can have drastic consequences for the material properties of nanowire shells. We expect that this finding holds good also for other alloy nanowire shells.

External Control of GaN Band Bending Using Phosphonate Self-Assembled Monolayers.

We report on the optoelectronic properties of GaN(0001) and (11̅00) surfaces after their functionalization with phosphonic acid derivatives. To analyze the possible correlation between the acid's electronegativity and the GaN surface band bending, two types of phosphonic acids, n-octylphosphonic acid (OPA) and 1H,1H,2H,2H-perfluorooctanephosphonic acid (PFOPA), are grafted on oxidized GaN(0001) and GaN(11̅00) layers as well as on GaN nanowires. The resulting hybrid inorganic/organic heterostructures are investigated by X-ray photoemission and photoluminescence spectroscopy. The GaN work function is changed significantly by the grafting of phosphonic acids, evidencing the formation of dense self-assembled monolayers. Regardless of the GaN surface orientation, both types of phosphonic acids significantly impact the GaN surface band bending. A dependence on the acids' electronegativity is, however, only observed for the oxidized GaN(11̅00) surface, indicating a relatively low density of surface states and a favorable band alignment between the surface oxide and acids' electronic states. Regarding the optical properties, the covalent bonding of PFOPA and OPA on oxidized GaN layers and nanowires significantly affects their internal quantum efficiency, especially in the nanowire case due to the large surface-to-volume ratio. The variation in the internal quantum efficiency is related to the modification of both the internal electric fields and surface states. These results demonstrate the potential of phosphonate chemistry for the surface functionalization of GaN, which could be exploited for selective sensing applications.

National Publication Productivity during the COVID-19 Pandemic-A Preliminary Exploratory Analysis of the 30 Countries Most Affected.

BACKGROUND: The COVID 19 pandemic increased publication productivity enormously with numerous new COVID-19-related articles appearing daily, despite the fact that many health care workers in the partially overburdened national health care systems were faced with major challenges. METHODS: In a cross-sectional, observational, retrospective study we compared and correlated 17 epidemiologic, health care system-related and health-economic factors from medical databases and intergovernmental organisations potentially influencing the COVID-19 and non-COVID-19 publication productivity between 1 January and 30 April 2020 amongst the 30 countries most severely affected by the pandemic. These factors were additionally correlated with the national pre-COVID-19 publication rate for the same pre-year period to identify potential changes in the general publication behaviour. FINDINGS: COVID-19 and non-COVID-19 publication rates correlated strongest with access to and quality of health care (ρ = 0.80 and 0.87, p < 0.0001), COVID-19 cases per capita (ρ = 0.78 and 0.72, p < 0.0001), GDP per capita (ρ = 0.69 and 0.76, p < 0.0001), health spending per capita (ρ = 0.61 and 0.73, p < 0.0001) and the pre-COVID-19 Hirsch-Index (ρ = 0.61 and 0.62, p = 0.002 and <0.0001). Ratios of publication rates for "Cancer", "Diabetes" and "Stroke" in 2020 versus the pre-year period were 0.88 ± 0.06, 1.02 ± 0.18 and 0.9 ± 0.20, resulting in a pooled ratio of 0.93 ± 0.06 for non-COVID-19 publications. INTERPRETATION: There are marked geographic and national differences in publication productivity during the COVID-19 pandemic. Both COVID-19- and non-COVID-19 publication productivity correlates with epidemiologic, health care system-related and healtheconomic factors, and pre-COVID publication expertise. Countries with a stable scientific infrastructure appear to maintain non-COVID-19 publication productivity nearly at the pre-year level and at the same time use their resilience to produce COVID-19 publications at high rates.

Internet and social media use in dermatology patients: Search behavior and impact on patient-physician relationship.

The traditional patient-physician relationship is being changed by the patients' searches for medical information on the Internet and in social media (SM). Freely available medical information online bears enormous potential but also holds dangers. In this cross-sectional, questionnaire-based study, the patients' motivation, preferences and unmet needs when searching for medical information online and the impact on the patient-physician relationship were assessed using Spearman's correlation coefficients, χ2 -tests and paired t-tests. Among 460 participants, 82.4% had already used the Internet/SM to gain medical information, but in only 9.4% their dermatologists had raised this topic. Online search for medical information was associated with female gender (P = .048), a higher skin-related burden (P = .020), higher level of education (P = .072), higher income (P = .019), anxiety (P = .004), and adnexal skin diseases (P = .043). For 16.1% of patients, "the Internet/SM" was their most important source of medical information; 81.4% deemed the impact of their online searches on their patient-physician relationship as neutral, 16.0% as positive, 2.6% as negative. The patients' top three unmet needs were "Online consultations", "Professional content on YouTube" and "Chat opportunities". Online search for medical information is a very important topic for most dermatology patients but it may not be adequately addressed by dermatologists. Our results indicate that from the patients`perspective such online searches do not have a significant impact on patient-physician relationship.

Corrigendum: Optical properties of GaN nanowires grown on chemical vapor deposited-graphene (2019 Nanotechnology 30 214005).

no abstract.

Global Trends in YouTube and Google Search Activity for Psoriasis and Atopic Eczema: Detecting Geographic Hot Spots, Blind Spots and Treatment Strategies.

To date, the geographical distribution and global trends of search activities on psoriasis and atopic eczema on Google and YouTube are widely unknown. The aim of this study was to identify geographic and temporal trends in YouTube and Google search activities for psoriasis and atopic eczema. We used specific filter settings on Google Trends to indicate the global search activity for ("Psoriasis") and ("Atopic Eczema") on Google and YouTube between January 1st , 2008 and August 7th , 2019. The four resulting data sets were analyzed and compared with respect to geographic distribution and temporal trends. Apart from a few "blind spots" (eg, Chad, Uzbekistan) the term "Psoriasis" was queried geographically fairly evenly distributed. The opposite was true for "Atopic Eczema", which was predominantly queried from a few "hot spots" (eg, United States, Commonwealth of Nations and Sweden). Since 2008, the search activity on YouTube for "Psoriasis" has tripled, while that for "Atopic Eczema" has decreased. On Google, by contrast, search activity has risen for both "Psoriasis" and "Atopic Eczema." Google Trends can be a useful tool to track people's/patients' interests and search search behavior over time, enabling, for instance, regionally tailored information and prevention campaigns.

Fiction, Falsehoods, and Few Facts: Cross-Sectional Study on the Content-Related Quality of Atopic Eczema-Related Videos on YouTube.

BACKGROUND: In recent years, YouTube has become a recognized source of medical information for health care consumers. Although YouTube has advantages in this context, there are potential dangers as videos may contain nonscientific, misleading, or even harmful information. OBJECTIVE: As little is known about YouTube as a source of information on atopic dermatitis (AD), we investigated the content-related quality of AD videos and their perception among YouTube users. METHODS: The quality of the 100 most viewed AD videos was assessed by using the Global Quality Scale (GQS) and the DISCERN instrument. Videos were classified as "useful," "misleading," and "potentially harmful," and the correlations of viewers' ratings (likes) with the GQS and DISCERN scores were assessed. RESULTS: Among the 100 videos, 68.0% (68/100) and 62.0% (62/100) were of poor and very poor scientific quality, respectively. Additionally, 32.0% (32/100) of the videos were classified as useful, 48.0% (48/100) were classified as misleading, and 34.0% (34/100) were classified as potentially harmful. Viewers' ratings did not correlate with the GQS and DISCERN scores. Overall, 50.0% (50/100) of the videos were posted by private individuals and promoters of complementary/alternative treatments, 42.0% (42/100) by therapeutical advertisers, and only 8.0% (8/100) by nonprofit organizations/universities. CONCLUSIONS: Our study demonstrated that two-thirds of the videos analyzed were below acceptable medical quality standards and that many videos were disseminating misleading or even dangerous content. Subjective and anecdotal content was overrepresented, and viewers did not appear to be able to distinguish between high- and low-quality videos. Health promotion strategies by professional medical organizations are needed to improve their presence and visibility on YouTube.

Sexually transmitted coinfections in patients with anogenital warts - a retrospective analysis of 196 patients.

BACKGROUND AND OBJECTIVES: Anogenital warts (AGWs) are most commonly caused by low-risk human papillomavirus (HPV) types, and although they are the most frequent viral sexually transmitted infections (STIs), little is known about STI coinfections in affected patients. We therefore sought to assess STI coinfection rates in patients with AGW, specify STI coinfections and calculate the number needed to screen (NNS) for each STI. METHODS: A retrospective cross-sectional study analyzing data sets from AGW patients treated in our clinic between 2008-2016. RESULTS: 142/196 (72 %) patients had been variably screened for infections with HIV, HBV and HCV, Treponema pallidum, Neisseria gonorrhoeae, Chlamydia trachomatis, Mycoplasma genitalium and HSV. The STI coinfection rate in all tested patients was 24.6 %, yielding an NNS of 4.1 to detect any STI. Of note, the coinfection rate did not differ significantly between heterosexual men, homosexual men and women, respectively. The NNS for syphilis was 8.4, for HIV 14.0, for HCV 28.5 and for HBV 39.0. The NNS for asymptomatic patients tested for HSV, Chlamydia trachomatis and Mycoplasma genitalium were 1.4, 5.3 and 12.0, respectively. CONCLUSION: Due to the high prevalence of STI coinfections, AGW patients should be screened for other STIs.