Spin orbit coupling at the level of a single electron

We utilize electron counting techniques to distinguish a spin conserving fast tunneling process and a slower process involving spin flips in AlGaAs/GaAs-based double quantum dots. By studying the dependence of the rates on the interdot tunnel coupling of the two dots, we find that as many as 4% of the tunneling events occur with a spin flip related to spin-orbit coupling in GaAs. Our measurement has a fidelity of 99 % in terms of resolving whether a tunneling event occurred with a spin flip or not

Stable Branched Electron Flow

The pattern of branched electron flow revealed by scanning gate microscopy shows the distribution of ballistic electron trajectories. The details of the pattern are determined by the correlated potential of remote dopants with an amplitude far below the Fermi energy. We find that the pattern persists even if the electron density is significantly reduced such that the change in Fermi energy exceeds the background potential amplitude. The branch pattern is robust against changes in charge carrier density, but not against changes in the background potential caused by additional illumination of the sample.Comment: Accepted for publication in New Journal of Physic

Stellenwert der minimal-invasiven Chirurgie beim primären und sekundären Hyperparathyroidismus

BACKGROUND: The standard surgical approach to treat primary (pHPT) and secondary hyperparathyroidism (sHPT) used to be a cervicotomy with exploration of all four parathyroid glands. This access has been challenged recently by the introduction of minimally invasive techniques in order to achieve superior cosmesic results and to reduce theatre time. We analyzed the advantages and morbidities of these surgical aproaches. PATIENTS AND METHODS: Between 1997 and 2006 a total of 123 patients (109 with pHPT and 14 with sHPT) underwent parathyroidectomy at the ENT Department in Luzern. Ultrasonographic scanning was performed on 74 patients (68%), szintigraphy in 8 patients (7%) and both scanning methods in 27 patients (25%). 103 patients were available for follow-up. The indications for each technique were reviewed and outcome measures included serum Calcium and parathyroid hormone levels. RESULTS: Sensitivity for preoperative ultrasonographic and scintigraphic scanning was 67% and 65% for identification of the correct quadrant and 74% and 71% for identification of the correct side. A bilateral exploration was performed until June 2001 for all patients. Thereafter, a minimally invasive approach was chosen for patients with pHPT, whereas patients with sHPT still require bilateral exploration. Adequate preoperative localization was a prerequisite for a minimally invasive technique. Mean postoperative serum Kalzium levels were within the normal range, independently of the surgical technique and disease. Two patients developed hypercalcemia after an initially successful operation. CONCLUSIONS: Review of the literature confirms the shift from bilateral exploration towards minimally invasive techniques. The incidence of persistent or recurrent disease as well as the rate of complications seems comparable. Operation time for minimally invasive techniques is reduced in the hands of an experienced surgeon. However, proper preoperative localization of the diseased parathyroid gland is not always possible and the expenses of intraoperative parathyroid hormone measures do not lower the overall costs. Considerable experience and a multidisiplinary approach (endocrinologist, surgeon, pathologist) is required to adopt efficient minimally invasive techniques. As for sHPT, bilateral exploration remains the treatment of choice

Temporal variation of pesticide mixtures in rivers of three agricultural watersheds during a major drought in the Western Cape, South Africa

South Africa is the leading pesticide user in Sub-Saharan Africa. However, little is known about the occurrence of pesticide mixtures in surface water and potential environmental risks in Africa. This study investigated the occurrence of pesticides mixtures in three watersheds during a drought year in South Africa. The study was conducted in the Krom River, Berg River and Hex River watersheds within larger agriculture systems in the Western Cape. Pesticide spray records were collected from 38 farms. A total of 21 passive water samplers (styrenedivinylbenzene disks (SDB)) were deployed, each for two weeks per month, over seven sampling rounds during the main pesticide application period between July 2017 and January 2018. Samples were analyzed for 248 pesticide compounds using LC-HR-MS/MS. Pesticide occurrence was analyzed for temporal agreement with pesticide spraying events (Cohen's kappa) and correlation with rainfall patterns and river discharge (Pearson correlation (r p )). Pesticide time-weighted average concentrations were estimated and compared to environmental quality standards (EQS). According to the farm spray records, 96 different pesticides were sprayed during the sampling period and differed considerably between the three study areas, seasons and crops grown. In total, 53 compounds were detected in river water. We detected 39% of compounds from the spraying records and demonstrated close temporal correlations of seasonal patterns for 11 pesticide compounds between reported on spraying records and observations in the streams (kappa = 0.90). However, 23 detected pesticides were not found on spray records, many of them being herbicides. Most of the estimated two-week average pesticide concentrations were below 40 ng/L. The insecticides imidacloprid, thiacloprid, chlorpyrifos and acetamiprid and the herbicide terbuthylazine exceeded at least once their EQS 58-fold (EQS 13 ng/L), 12-fold (EQS 10 ng/L), 9-fold (EQS 0.46 ng/L), 5-fold (EQS 24 ng/L) and 3-fold (EQS 220 ng/L), respectively. Our study substantially widens the view on pesticide pollution in surface water compared to previous studies in Sub-Saharan Africa by targeting more than 200 pesticides using passive sampling systems. This broad assessment revealed the presence of 53 compounds, some of them in high concentrations, indicating possible adverse effects on biota and the quality of the ecosystem. Whether the observed concentration levels in the year 2017 were exceptional due to the lowest ever recorded rainfall and river discharge needs to be tested with additional data to better understand how pesticide pollution levels manifest under average rainfall and river discharge conditions

Cohort study on the effects of everyday life radio frequency electromagnetic field exposure on non-specific symptoms and tinnitus

BACKGROUND: There is public concern regarding potential health effects of radio frequency electromagnetic fields (RF-EMF) exposure, as produced by mobile phones or broadcast transmitters. The objective of this study was to investigate the association between RF-EMF exposure and non-specific symptoms and tinnitus in a prospective cohort study. METHODS: In 2008, 1375 randomly selected participants from Basel, Switzerland, were enrolled in a questionnaire survey with follow-up after one year (participation rate 82%). A score for somatic complaints (von Zerssen list) and headache (HIT-6) was assessed. Far-field environmental RF-EMF exposure was predicted using a validated prediction model. Regarding near-field exposure, self-reported mobile and cordless phone use as well as mobile phone operator data were collected. In multivariate regression models, we investigated whether exposure at baseline (cohort analysis) or changes in exposure between baseline and follow-up (change analysis) were related to changes in health scores. RESULTS: For participants in the top decile of environmental far-field RF-EMF exposure at baseline, in comparison to participants exposed below the median value, the change in the von Zerssen- and HIT-6-scores between baseline and follow-up was -0.12 (95%-CI: -1.79 to 1.56) and -0.37 (95%-CI: -1.80 to 1.07) units, respectively. Exposure to near-field sources and a change in exposure between baseline and follow-up were not related to non-specific symptoms. Similarly, no association between RF-EMF exposure and tinnitus was observed. CONCLUSIONS: In this first cohort study using objective and well-validated RF-EMF exposure measures, we did not observe an association between RF-EMF exposure and non-specific symptoms or tinnitu

Classification of personal exposure to radio frequency electromagnetic fields (RF-EMF) for epidemiological research : evaluation of different exposure assessment methods

The use of personal exposure meters (exposimeters) has been recommended for measuring personal exposure to radio frequency electromagnetic fields (RF-EMF) from environmental far-field sources in everyday life. However, it is unclear to what extent exposimeter readings are affected by measurements taken when personal mobile and cordless phones are used. In addition, the use of exposimeters in large epidemiological studies is limited due to high costs and large effort for study participants. In the current analysis we aimed to investigate the impact of personal phone use on exposimeter readings and to evaluate different exposure assessment methods potentially useful in epidemiological studies. We collected personal exposimeter measurements during one week and diary data from 166 study participants. Moreover, we collected spot measurements in the participants' bedrooms and data on self-estimated exposure, assessed residential exposure to fixed site transmitters by calculating the geo-coded distance and mean RF-EMF from a geospatial propagation model, and developed an exposure prediction model based on the propagation model and exposure relevant behavior. The mean personal exposure was 0.13mW/m(2), when measurements during personal phone calls were excluded and 0.15mW/m(2), when such measurements were included. The Spearman correlation with personal exposure (without personal phone calls) was 0.42 (95%-CI: 0.29 to 0.55) for the spot measurements, -0.03 (95%-CI: -0.18 to 0.12) for the geo-coded distance, 0.28 (95%-CI: 0.14 to 0.42) for the geospatial propagation model, 0.50 (95%-CI: 0.37 to 0.61) for the full exposure prediction model and 0.06 (95%-CI: -0.10 to 0.21) for self-estimated exposure. In conclusion, personal exposure measured with exposimeters correlated best with the full exposure prediction model and spot measurements. Self-estimated exposure and geo-coded distance turned out to be poor surrogates for personal exposure

Current use pesticides in soil and air from two agricultural sites in South Africa: implications for environmental fate and human exposure

Concerns about the possible negative impacts of current use pesticides (CUPs) for both the environment and human health have increased worldwide. However, the knowledge on the occurrence of CUPs in soil and air and the related human exposure in Africa is limited. This study investigated the presence of 30 CUPs in soil and air at two distinct agricultural sites in South Africa and estimated the human exposure and related risks to rural residents via soil ingestion and inhalation (using hazard quotients, hazard index and relative potency factors). We collected 12 soil and 14 air samples over seven days during the main pesticide application season in 2018. All samples were extracted, purified and analyzed by high-performance liquid chromatography coupled with tandem mass spectrometry. In soils, nine CUPs were found, with chlorpyrifos, carbaryl and tebuconazole having the highest concentrations (up to 63.6, 1.10 and 0.212 ng g(-1), respectively). In air, 16 CUPs were found, with carbaryl, tebuconazole and terbuthylazine having the highest levels (up to 25.0, 22.2 and 1.94 pg m(-3), respectively). Spatial differences were observed between the two sites for seven CUPs in air and two in soils. A large dominance towards the particulate phase was found for almost all CUPs, which could be related to mass transport kinetics limitations (non-equilibrium) following pesticide application. The estimated daily intake via soil ingestion and inhalation of individual pesticides ranged from 0.126 fg kg(-1) day(-1) (isoproturon) to 14.7 ng kg(-1) day(-1) (chlorpyrifos). Except for chlorpyrifos, soil ingestion generally represented a minor exposure pathway compared to inhalation (i.e. <5%). The pesticide environmental exposure largely differed between the residents of the two distinct agricultural sites in terms of levels and composition. The estimated human health risks due to soil ingestion and inhalation of pesticides were negligible although future studies should explore other relevant pathways

Spatial and temporal variations in PM10 concentrations between 2010-2017 in South Africa

Particulate matter less than or equal to 10 mum in aerodynamic diameter (PM10 microg/m(3)) is a priority air pollutant and one of the most widely monitored ambient air pollutants in South Africa. This study analyzed PM10 from monitoring 44 sites across four provinces of South Africa (Gauteng, Mpumalanga, Western Cape and KwaZulu-Natal) and aimed to present spatial and temporal variation in the PM10 concentration across the provinces. In addition, potential influencing factors of PM10 variations around the three site categories (Residential, Industrial and Traffic) were explored. The spatial trend in daily PM10 concentration variation shows PM10 concentration can be 5.7 times higher than the revised 2021 World Health Organization annual PM10 air quality guideline of 15 microg/m(3) in Gauteng province during the winter season. Temporally, the highest weekly PM10 concentrations of 51.4 microg/m(3), 46.8 microg/m(3), 29.1 microg/m(3) and 25.1 microg/m(3) at Gauteng, Mpumalanga, KwaZulu-Natal and Western Cape Province were recorded during the weekdays. The study results suggest a decrease in the change of annual PM10 levels at sites in Gauteng and Mpumalanga Provinces. An increased change in annual PM10 levels was reported at most sites in Western Cape and KwaZulu-Natal

Association of transportation noise with sleep during the first year of life: a longitudinal study

STUDY OBJECTIVES: During infancy, adequate sleep is crucial for physical and neurocognitive development. In adults and children, night-time noise exposure is associated with sleep disturbances. However, whether and to what extent infants' sleep is affected, is unknown. Thus, this study investigated the relationship between nocturnal transportation noise and actimetry-derived habitual sleep behavior across the first year of life. METHODS: In 144 healthy infants (63 girls), nocturnal (23:00-7:00) transportation noise (i.e., road, railway, and aircraft) was modelled at the infants' individual places of residence. Using actimetry, we recorded movement patterns for 11 days in a longitudinal design at 3, 6, and 12 months of age and derived the recently proposed core sleep composites of night-time sleep duration, activity, and variability. Using linear mixed-effects models, we determined associations between noise exposure and sleep composites. Sex, gestational age, parents' highest educational level, infants' age, and the existence of siblings served as control variables. RESULTS: In models without interactions, night-time transportation noise was unrelated to sleep composites across the first year of life (p > .16). Exploratory analyses of an interaction between noise and the existence of siblings yielded an association between night-time transportation noise and sleep duration in infants without siblings only (p = .004). CONCLUSION: In our study, sleep in infants during the first year of life was relatively robust against external perturbation by night-time transportation noise. However, particularly in children without siblings increasing night-time transportation noise reduced sleep duration. This suggests that the habitual noise environment may modulate individual susceptibility to adverse effects of noise on sleep