Teaching breast ultrasound skills including core-needle biopsies on a phantom enhances undergraduate student's knowledge and learning satisfaction.

PURPOSE: To investigate whether a training program on breast ultrasound skills including core-needle biopsies to undergraduate students can improve medical knowledge and learning satisfaction. METHODS: Medical students attending mandatory classes at the Medical School of the University of Saarland received a supplemental theoretical and hands-on training program on ultrasound (US) breast screening and on US-guided core-needle biopsy using an agar-agar phantom. Experienced breast specialists and ultrasound examiners served as trainers applying Peyton's 4-step training approach. The students' theoretical knowledge and hands-on skills were tested before and after the training program, using a multiple-choice questionnaire (MCQ), the Objective Structured Clinical Examination (OSCE) and a student curriculum evaluation. RESULTS: The MCQ results showed a significant increase of the student's theoretical knowledge (50.2-75.2%, p < 0.001). After the course, the OSCE showed a mean total of 17.3/20 points (86.5%), confirming the practical implementation of the new skills. The student curriculum evaluation in general was very positive. A total of 16/20 questions were rated between 1.2 and 1.7 (very good) and 3 questions were rated as 2.1 (good). CONCLUSION: Undergraduate student's medical education can be enhanced by teaching breast US skills.

An Assessment of Earth's Climate Sensitivity Using Multiple Lines of Evidence.

We assess evidence relevant to Earth's equilibrium climate sensitivity per doubling of atmospheric CO2, characterized by an effective sensitivity S. This evidence includes feedback process understanding, the historical climate record, and the paleoclimate record. An S value lower than 2 K is difficult to reconcile with any of the three lines of evidence. The amount of cooling during the Last Glacial Maximum provides strong evidence against values of S greater than 4.5 K. Other lines of evidence in combination also show that this is relatively unlikely. We use a Bayesian approach to produce a probability density function (PDF) for S given all the evidence, including tests of robustness to difficult-to-quantify uncertainties and different priors. The 66% range is 2.6-3.9 K for our Baseline calculation and remains within 2.3-4.5 K under the robustness tests; corresponding 5-95% ranges are 2.3-4.7 K, bounded by 2.0-5.7 K (although such high-confidence ranges should be regarded more cautiously). This indicates a stronger constraint on S than reported in past assessments, by lifting the low end of the range. This narrowing occurs because the three lines of evidence agree and are judged to be largely independent and because of greater confidence in understanding feedback processes and in combining evidence. We identify promising avenues for further narrowing the range in S, in particular using comprehensive models and process understanding to address limitations in the traditional forcing-feedback paradigm for interpreting past changes.

Laparoscopic Liver Resection: A South American Experience with 2887 Cases.

BACKGROUND: Laparoscopic liver resections (LLR) have been increasingly performed in recent years. Most of the available evidence, however, comes from specialized centers in Asia, Europe and USA. Data from South America are limited and based on single-center experiences. To date, no multicenter studies evaluated the results of LLR in South America. The aim of this study was to evaluate the experience and results with LLR in South American centers. METHODS: From February to November 2019, a survey about LLR was conducted in 61 hepatobiliary centers in South America, composed by 20 questions concerning demographic characteristics, surgical data, and perioperative results. RESULTS: Fifty-one (83.6%) centers from seven different countries answered the survey. A total of 2887 LLR were performed, as follows: Argentina (928), Brazil (1326), Chile (322), Colombia (210), Paraguay (9), Peru (75), and Uruguay (8). The first program began in 1997; however, the majority (60.7%) started after 2010. The percentage of LLR over open resections was 28.4% (4.4-84%). Of the total, 76.5% were minor hepatectomies and 23.5% major, including 266 right hepatectomies and 343 left hepatectomies. The conversion rate was 9.7%, overall morbidity 13%, and mortality 0.7%. CONCLUSIONS: This is the largest study assessing the dissemination and results of LLR in South America. It showed an increasing number of centers performing LLR with the promising perioperative results, aligned with other worldwide excellence centers.

Everolimus- vs. novolimus-eluting bioresorbable scaffolds in patients with acute coronary syndrome.

BACKGROUND: Limited data exist on bioresorbable scaffolds (BRS) in patients with acute coronary syndrome (ACS). The aim of the present study was to evaluate novolimus-eluting BRS (DESolve) as interventional treatment for patients with ACS, and to compare its 12-month outcomes with the everolimus-eluting bioresorbable scaffolds (Absorb). METHODS: In this retrospective study, patients with ACS (including unstable angina pectoris, ST-segment elevation myocardial infarction, or non-ST-segment elevation myocardial infarction) treated with either the Absorb or the DESolve BRS were evaluated in a 1:1 matched-pair analysis. Major adverse cardiac events (MACE), including death, myocardial infarction, and target lesion revascularization, were evaluated as a major endpoint. The occurrence of scaffold thrombosis was also assessed. RESULTS: A total of 102 patients were eligible for this analysis. The rate of MACE at 12 months was comparable between the Absorb and the DESolve group (8.3% vs. 6.8%, p = 0.738). The occurrence of target lesion revascularization (6.2% vs. 4.7%; p = 0.700) and scaffold thrombosis (4.1% vs. 2.1%; p = 0.580) was comparable as well. All instances of scaffold thrombosis occurred within 30 days of the index procedure. CONCLUSION: In this study, similar 12-month event rates were observed for both BRS types after implantation for the treatment of ACS.

Fetal heart rate variability responsiveness to maternal stress, non-invasively detected from maternal transabdominal ECG.

PURPOSE: Prenatal stress (PS) during pregnancy affects in utero- and postnatal child brain-development. Key systems affected are the hypothalamic-pituitary-adrenal axis and the autonomic nervous system (ANS). Maternal- and fetal ANS activity can be gauged non-invasively from transabdominal electrocardiogram (taECG). We propose a novel approach to assess couplings between maternal (mHR) and fetal heart rate (fHR) as a new biomarker for PS based on bivariate phase-rectified signal averaging (BPRSA). We hypothesized that PS exerts lasting impact on fHR. METHODS: Prospective case-control study matched for maternal age, parity, and gestational age during the third trimester using the Cohen Perceived Stress Scale (PSS-10) questionnaire with PSS-10 over or equal 19 classified as stress group (SG). Women with PSS-10 < 19 served as control group (CG). Fetal electrocardiograms were recorded by a taECG. Coupling between mHR and fHR was analyzed by BPRSA resulting in fetal stress index (FSI). Maternal hair cortisol, a memory of chronic stress exposure for 2-3 months, was measured at birth. RESULTS: 538/1500 pregnant women returned the questionnaire, 55/538 (10.2%) mother-child pairs formed SG and were matched with 55/449 (12.2%) consecutive patients as CG. Maternal hair cortisol was 86.6 (48.0-169.2) versus 53.0 (34.4-105.9) pg/mg (p = 0.029). At 36 + 5 weeks, FSI was significantly higher in fetuses of stressed mothers when compared to controls [0.43 (0.18-0.85) versus 0.00 (- 0.49-0.18), p < 0.001]. CONCLUSION: Prenatal maternal stress affects the coupling between maternal and fetal heart rate detectable non-invasively a month prior to birth. Lasting effects on neurodevelopment of affected offspring should be studied. TRIAL REGISTRATION: Clinical trial registration: NCT03389178.

Subtle ocular movements in a patient with brain death.

Introduction and Case Presentation: Brain death can be associated with limb movements that are attributed to spinal reflexes. Although head/face movements have been rarely reported, no case of overt eye movements in brain death has been documented. We report a case of a patient with subtle eye movements whose exam was otherwise consistent with brain death. The presence of eye movements delayed pronouncing the patient as brain dead and delayed organ donation. We agree with American Academy of Neurology Position statement from 2019 that brain death does not mean demise of every neuron. Discussion: This case raises important questions about the types of movements that should be "allowed" during the determination of brain death to avoid delays in diagnosis.

Efficacy and safety of two post-operative drains: results of a prospectively randomized clinical study in breast cancer patients after breast conserving surgery.

OBJECTIVE: To compare the efficacy and safety of two post-operative drains in breast cancer patients after breast conserving surgery. METHODS: This was a prospectively randomized comparative study of two drains investigated in breast cancer patients after breast conserving therapy. The Redon drain ends in a tip with 28 double perforations while the Quadrain drain features 4 flexible flaps of about 0.15 m length. The drains cost 0.28 € and 3.54 €, respectively. Primary target parameter was the duration of the drains staying in the surgical site. Secondary target parameters were pain post-surgery, seroma volume, final cosmetic result and surgical site infections. RESULTS: A total of 88 patients were randomized, 47 and 41 received the Redon drain and the Quadrain drain, respectively. The mean duration of the drains staying in the surgical site was not different between the Redon and the Quadrain drain, 42.6 h (± 25.8 h) and 50.1 h (± 28.5 h), respectively (p = 0.1959). The post-operative pain score, seroma size, cosmetic result and surgical site infections were not different for both systems. CONCLUSION: The Redon drain and the new Quadrain drain were not significantly different with respect to duration in the surgical site, post-operative pain, seroma volume and cosmetic result.

Rare compound heterozygous variants in PNKP identified by whole exome sequencing in a German patient with ataxia-oculomotor apraxia 4 and pilocytic astrocytoma.

Ataxia-oculomotor apraxia type 4 (AOA4) is a rare autosomal recessive neurologic disorder. The phenotype is characterized by ataxia, oculomotor apraxia, peripheral neuropathy and dystonia. AOA4 is caused by biallelic pathogenic variants in the PNKP gene encoding a polynucleotide kinase 3'-phosphatase with an important function in DNA-damage repair. By whole exome sequencing, we identified 2 variants within the PNKP gene in a 27-year-old German woman with a clinical AOA phenotype combined with a cerebellar pilocytic astrocytoma diagnosed at 23 years of age. One variant, a duplication in exon 14 resulting in the frameshift c.1253_1269dup p.(Thr424fs*49), has previously been described as pathogenic, for example, in cases of AOA4. The second variant, representing a nonsense mutation in exon 17, c.1545C>G p.(Tyr515*), has not yet been described and is predicted to cause a loss of the 7 C-terminal amino acids. This is the first description of AOA4 in a patient with central European descent. Furthermore, the occurrence of a pilocytic astrocytoma has not been described before in an AOA4 patient. Our data demonstrate compound heterozygous PNKP germline variants in a German patient with AOA4 and provide evidence for a possible link with tumor predisposition. Localization of the 2 variants in human PNKP NP_009185.2. NM_007254.3:c.1253_1269dup p.(Thr424fs*49) is predicted to cause a frameshift within the kinase domain, NM_007254.3:c.1545C>G p.(Tyr515*) is predicted to cause loss of 2 C-terminal amino acids of the kinase domain and 5 additional C-terminal amino acids.

Influence of gestational diabetes on fetal autonomic nervous system: a study using phase-rectified signal-averaging analysis.

OBJECTIVES: Maternal gestational diabetes mellitus (GDM) is known to influence fetal physiology. Phase-rectified signal averaging (PRSA) is an innovative signal-processing technique that can be used to investigate fetal heart signals. The PRSA-calculated variables average acceleration capacity (AAC) and average deceleration capacity (ADC) are established indices of autonomic nervous system (ANS) function. The aim of this study was to evaluate the influence of GDM on the fetal cardiovascular and ANS function in human pregnancy using PRSA. METHODS: This was a prospective clinical case-control study of 58 mothers with diagnosed GDM and 58 gestational-age matched healthy controls in the third trimester of pregnancy. Fetal cardiotocography (CTG) recordings were performed in all cases at entry to the study, and a follow-up recording was performed in 19 GDM cases close to delivery. The AAC and ADC indices were calculated by the PRSA method and fetal heart rate short-term variation (STV) by CTG software according to Dawes-Redman criteria. RESULTS: Mean gestational age of both groups at study entry was 35.7 weeks. There was a significant difference in mean AAC (1.97 ± 0.33 bpm vs 2.42 ± 0.57 bpm; P < 0.001) and ADC (1.94 ± 0.32 bpm vs 2.28 ± 0.46 bpm; P < 0.001) between controls and fetuses of diabetic mothers. This difference could not be demonstrated using standard computerized fetal CTG analysis of STV (controls, 10.8 ± 3.0 ms vs GDM group, 11.3 ± 2.5 ms; P = 0.32). Longitudinal fetal heart rate measurements in a subgroup of women with diabetes were not significantly different from those at study entry. CONCLUSIONS: Our findings show increased ANS activity in fetuses of diabetic mothers in late gestation. Analysis of human fetal cardiovascular and ANS function by PRSA may offer improved surveillance over conventional techniques linking GDM pregnancy to future cardiovascular dysfunction in the offspring. Copyright © 2017 ISUOG. Published by John Wiley & Sons Ltd.

Intratumoural evolutionary landscape of high-risk prostate cancer: the PROGENY study of genomic and immune parameters.

BACKGROUND: Intratumoural heterogeneity (ITH) is well recognised in prostate cancer (PC), but its role in high-risk disease is uncertain. A prospective, single-arm, translational study using targeted multiregion prostate biopsies was carried out to study genomic and T-cell ITH in clinically high-risk PC aiming to identify drivers and potential therapeutic strategies. PATIENTS AND METHODS: Forty-nine men with elevated prostate-specific antigen and multiparametric-magnetic resonance imaging detected PC underwent image-guided multiregion transperineal biopsy. Seventy-nine tumour regions from 25 patients with PC underwent sequencing, analysis of mutations, copy number and neoepitopes combined with tumour infiltrating T-cell subset quantification. RESULTS: We demonstrated extensive somatic nucleotide variation and somatic copy number alteration heterogeneity in high-risk PC. Overall, the mutational burden was low (0.93/Megabase), but two patients had hypermutation, with loss of mismatch repair (MMR) proteins, MSH2 and MSH6. Somatic copy number alteration burden was higher in patients with metastatic hormone-naive PC (mHNPC) than in those with high-risk localised PC (hrlPC), independent of Gleason grade. Mutations were rarely ubiquitous and mutational frequencies were similar for mHNPC and hrlPC patients. Enrichment of focal 3q26.2 and 3q21.3, regions containing putative metastasis drivers, was seen in mHNPC patients. We found evidence of parallel evolution with three separate clones containing activating mutations of ß-catenin in a single patient. We demonstrated extensive intratumoural and intertumoural T-cell heterogeneity and high inflammatory infiltrate in the MMR-deficient (MMRD) patients and the patient with parallel evolution of ß-catenin. Analysis of all patients with activating Wnt/ß-catenin mutations demonstrated a low CD8+/FOXP3+ ratio, a potential surrogate marker of immune evasion. CONCLUSIONS: The PROGENY (PROstate cancer GENomic heterogeneitY) study provides a diagnostic platform suitable for studying tumour ITH. Genetic aberrations in clinically high-risk PC are associated with altered patterns of immune infiltrate in tumours. Activating mutations of Wnt/ß-catenin signalling pathway or MMRD could be considered as potential biomarkers for immunomodulation therapies. CLINICAL TRIALS.GOV IDENTIFIER: NCT02022371.

iDermatoPath - a novel software tool for mitosis detection in H&E-stained tissue sections of malignant melanoma.

BACKGROUND: Malignant Melanoma (MM) is characterized by a growing incidence and a high malignant potential. Besides well-defined prognostic factors such as tumour thickness and ulceration, the Mitotic Rate (MR) was included in the AJCC recommendations for diagnosis and treatment of MM. In daily routine, the identification of a single mitosis can be difficult on haematoxylin and eosin slides alone. Several studies showed a big inter- and intra-individual variability in detecting the MR in MM even by very experienced investigators, thus raising the question for a computer-assisted method. OBJECTIVE: The objective was to develop a software system for mitosis detection in MM on H&E slides based on machine learning for diagnostic support. METHODS: We developed a computer-aided staging support system based on image analysis and machine learning on the basis of 59 MM specimens. Our approach automatically detects tumour regions, identifies mitotic nuclei and classifies them with respect to their diagnostic relevance. A convenient user interface enables the investigator to browse through the proposed mitoses for fast and efficient diagnosing. RESULTS: A quantitative evaluation on manually labelled ground truth data revealed that the tumour region detection yields a medium spatial overlap index (dice coefficient) of 0.72. For the mitosis detection, we obtained high accuracies of above 83%. CONCLUSION: On the technical side, the developed iDermatoPath software tool provides a novel approach for mitosis detection in MM, which can be further improved using more training data such as dermatopathologist annotations. On the practical side, a first evaluation of the clinical utility was positive, albeit this approach provides most benefit for difficult cases in a research setting. Assuming all slides to be digitally processed and reported in the near future, this method could become a helpful additional tool for the pathologist.

[Acute and chronic heart failure]. / Akute und chronische Herzinsuffizienz.

The initial therapy of chronic heart failure is still based on diuretics, angiotensin-converting enzyme (ACE) inhibitors, beta-blockers and in specific cases mineralocorticoid receptor antagonists. The new European Society of Cardiology (ESC) guidelines published in 2016 introduced angiotensin-receptor-neprilysin inhibitors, such as sacubitril/valsartan (LCZ 696) as new therapeutic agents in patients with chronic and progressive heart failure. New subgroup analyses for LCZ 696 have been published showing a beneficial effect in the context of various comorbidities, such as renal insufficiency, diabetes and hypotension. Furthermore, new data are available on intravenous iron substitution in chronic heart failure and on the indications for implantable converter defibrillators, cardiac resynchronization therapy and other cardiac devices. Medicinal therapy of acute heart failure is still limited. For patients who cannot be treated with medicinal therapy, mechanical circulatory support, such as extracorporeal membrane oxygenation (ECMO) should be recommended.

[Cleft lip and palate]. / Lippen-Kiefer-Gaumen-Spalten.

BACKGROUND: Cleft lip and palate (CLP) represents a group of malformations of unknown etiology but similar phenotypes. This implies consequences for the diagnostics, therapy, prevention, prognosis and risk estimation. OBJECTIVE: Definition of CLP subtypes and the embryonic development, clarification of correlations and differences between entities using epidemiological data, overview of the present state of genetic analyses, correlation to syndromes, sequences and associations and resulting consequences for clinical practice. MATERIAL AND METHODS: Update on embryological development of the face, summary of epidemiological and genetic studies and considerations on pedopathological and forensic aspects. RESULTS: Syndromic and non-syndromic CLP exhibit different and highly variable etiologies, therapeutic needs and prognosis. A thorough understanding is mandatory to distinguish between the different subgroups. In addition to specific aspects of CLP for the pediatric (forensic) pathologist this article provides an overall view of the topic which aims to help understand these malformations.

Optical Emission of Individual GaN Nanocolumns Analyzed with High Spatial Resolution.

Selective area growth has been applied to fabricate a homogeneous array of GaN nanocolumns (NC) with high crystal quality. The structural and optical properties of single NCs have been investigated at the nanometer-scale by transmission electron microscopy (TEM) and highly spatially resolved cathodoluminescence (CL) spectroscopy performed in a scanning transmission electron microscope (STEM) at liquid helium temperatures. TEM cross-section analysis reveals excellent structural properties of the GaN NCs. Sporadically, isolated basal plane stacking faults (BSF) can be found resulting in a remarkably low BSF density in the almost entire NC ensemble. Both, defect-free NCs and NCs with few BSFs have been investigated. The low defect density within the NCs allows the characterization of individual BSFs, which is of high interest for studying their optical properties. Direct nanometer-scale correlation of the CL and STEM data clearly exhibits a spatial correlation of the emission at 360.6 nm (3.438 eV) with the location of basal plane stacking faults of type I1.

[German Version of the Childbirth Self-Efficacy Inventory and its Short Form]. / Deutsche Version des Childbirth Self-Efficacy Inventory und dessen Kurzform - ein Fragebogen zur Selbstwirksamkeit.

BACKGROUND: The Childbirth Self-Efficacy Inventory (CBSEI) is an instrument that measures women's perceived self-efficacy towards labour. It is used in 9 countries, a 32-item short form (CBSEI-C32) in 4 countries. German versions of the CBSEI and the CBSEI-C32 have not been developed thus far. METHODS: A forward-backward translation was performed, followed by administration of both instruments to a sample of 155 participants of antenatal classes. Pregnant women answered questions regarding their medical history and user-friendliness of the instruments. 80 respondents completed the CBSEI, 75 the CBSEI-C32. Reliability via Cronbach alpha was calculated for the 4 subscales of the CBSEI and the 2 subscales of the short form. Validity was only assessed for the 2 scales of the CBSEI-C32 because all women (n=155) completed this instrument. RESULTS: 2 Cronbach alpha values were greater than 0.74 (adequate), the others greater than 0.80 (good). Most of the factors of the CBSEI-C32 (75%) were above ≥0.5. Calculation of the item-to-total-correlations revealed that the exclusion of 3 items might be indicated for the German version. The short form showed a significant association between level of education and perceived self-efficacy (p=0.01). RESULTS in the area of user-friendliness were more encouraging for the CBSEI-C32 than for the CBSEI. CONCLUSION: The German version of the CBSEI is a useful instrument which may improve advice and counselling during prenatal care in Germany.

Early detection of metastatic disease in asymptomatic breast cancer patients with whole-body imaging and defined tumour marker increase.

BACKGROUND: Follow-up care in breast cancer is still an issue of debate. Diagnostic methods are more sensitive, and more effective therapeutic options are now available. The risk of recurrence is not only influenced by tumour stage but also by the different molecular subtypes. This study was performed to evaluate the use of whole-body imaging combined with tumour marker monitoring for the early detection of asymptomatic metastatic breast cancer (MBC). METHODS: This analysis was performed as part of a follow-up study evaluating 813 patients with a median follow-up of 63 months. After primary therapy, all patients underwent tumour marker monitoring for CEA, CA 15-3 and CA 125 at 6-week intervals within an intensified diagnostic aftercare algorithm. A reproducible previously defined increase was considered as a strong indicator of MBC. From 2007 to 2010, 44 patients with tumour marker increase underwent whole-body magnetic resonance imaging and/or an FDG-PET/CT scan. Histological clarification and/or imaging follow-up were done. RESULTS: Metastases were detected in 65.9% (29/44) of patients, 13.6% (6/44) had secondary malignancies besides breast cancer and 20.5% (9/44) had no detectable malignancy. Limited disease was found in 24.1% (7/29) of patients. Median progression-free survival of MBC was 9.2 months and median overall survival was 41.1 months. The 3- and 5-year survival rates were 64.2% and 40.0%, respectively. CONCLUSIONS: A reproducible tumour marker increase followed by whole-body imaging is highly effective for early detection. By consequence, patients might benefit from earlier detection and improved therapeutic options with a prolonged survival.

Large-amplitude internal waves benefit corals during thermal stress.

Tropical scleractinian corals are particularly vulnerable to global warming as elevated sea surface temperatures (SSTs) disrupt the delicate balance between the coral host and their algal endosymbionts, leading to symbiont expulsion, mass bleaching and mortality. While satellite sensing of SST has proved a reliable predictor of coral bleaching at the regional scale, there are large deviations in bleaching severity and mortality on the local scale that are poorly understood. Here, we show that internal waves play a major role in explaining local coral bleaching and mortality patterns in the Andaman Sea. Despite a severe region-wide SST anomaly in May 2010, frequent upslope intrusions of cold sub-pycnocline waters due to breaking large-amplitude internal waves (LAIW) mitigated coral bleaching and mortality in shallow waters. In LAIW-sheltered waters, by contrast, bleaching-susceptible species suffered severe bleaching and total mortality. These findings suggest that LAIW benefit coral reefs during thermal stress and provide local refugia for bleaching-susceptible corals. LAIW are ubiquitous in tropical stratified waters and their swash zones may thus be important conservation areas for the maintenance of coral diversity in a warming climate. Taking LAIW into account can significantly improve coral bleaching predictions and provide a valuable tool for coral reef conservation and management.

Optical properties of strain-compensated CdSe/ZnSe/(Zn,Mg)Se quantum well microdisks.

Strain-compensated CdSe/ZnSe/(Zn,Mg)Se quantum well structures that were grown on (In,Ga)As allow for efficient room-temperature photoluminescence and spectral tuning over the whole visible range. We fabricated microdisk cavities from these samples by making use of a challenging chemical structuring technique for selective and homogeneous removal of the (In,Ga)As sacrificial layer below the quantum structure. The observed whispering gallery modes in our microdisks are mainly visible up to photon energies of ~ 2.3 eV due to strong self-absorption. As extinction coefficients and effective refractive indices are dominated by the quantum well material CdSe, thick quantum wells (> 3 monolayer) are necessary to observe resonances in the corresponding quantum well emission.

Is ice-rafted sediment in a North Pole marine record evidence for perennial sea-ice cover?

Ice-rafted sediments of Eurasian and North American origin are found consistently in the upper part (13 Ma BP to present) of the Arctic Coring Expedition (ACEX) ocean core from the Lomonosov Ridge, near the North Pole (≈88° N). Based on modern sea-ice drift trajectories and speeds, this has been taken as evidence of the presence of a perennial sea-ice cover in the Arctic Ocean from the middle Miocene onwards (Krylov et al. 2008 Paleoceanography 23, PA1S06. (doi:10.1029/2007PA001497); Darby 2008 Paleoceanography 23, PA1S07. (doi:10.1029/2007PA001479)). However, other high latitude land and marine records indicate a long-term trend towards cooling broken by periods of extensive warming suggestive of a seasonally ice-free Arctic between the Miocene and the present (Polyak et al. 2010 Quaternary Science Reviews 29, 1757-1778. (doi:10.1016/j.quascirev.2010.02.010)). We use a coupled sea-ice slab-ocean model including sediment transport tracers to map the spatial distribution of ice-rafted deposits in the Arctic Ocean. We use 6 hourly wind forcing and surface heat fluxes for two different climates: one with a perennial sea-ice cover similar to that of the present day and one with seasonally ice-free conditions, similar to that simulated in future projections. Model results confirm that in the present-day climate, sea ice takes more than 1 year to transport sediment from all its peripheral seas to the North Pole. However, in a warmer climate, sea-ice speeds are significantly faster (for the same wind forcing) and can deposit sediments of Laptev, East Siberian and perhaps also Beaufort Sea origin at the North Pole. This is primarily because of the fact that sea-ice interactions are much weaker with a thinner ice cover and there is less resistance to drift. We conclude that the presence of ice-rafted sediment of Eurasian and North American origin at the North Pole does not imply a perennial sea-ice cover in the Arctic Ocean, reconciling the ACEX ocean core data with other land and marine records.

Resonant generation of propagating second-harmonic spin waves in nano-waveguides.

Generation of second-harmonic waves is one of the universal nonlinear phenomena that have found numerous technical applications in many modern technologies, in particular, in photonics. This phenomenon also has great potential in the field of magnonics, which considers the use of spin waves in magnetic nanostructures to implement wave-based signal processing and computing. However, due to the strong frequency dependence of the phase velocity of spin waves, resonant phase-matched generation of second-harmonic spin waves has not yet been achieved in practice. Here, we show experimentally that such a process can be realized using a combination of different modes of nano-sized spin-wave waveguides based on low-damping magnetic insulators. We demonstrate that our approach enables efficient spatially-extended energy transfer between interacting waves, which can be controlled by the intensity of the initial wave and the static magnetic field.