Impact ionization induced by terahertz radiation in HgTe quantum wells of critical thickness

We report on the observation of terahertz (THz) radiation induced band-to-band impact ionization in \HgTe quantum well (QW) structures of critical thickness, which are characterized by a nearly linear energy dispersion. The THz electric field drives the carriers initializing electron-hole pair generation. The carrier multiplication is observed for photon energies less than the energy gap under the condition that the product of the radiation angular frequency $\omega$ and momentum relaxation time $\tau_{\text l}$ larger than unity. In this case, the charge carriers acquire high energies solely because of collisions in the presence of a high-frequency electric field. The developed microscopic theory shows that the probability of the light impact ionization is proportional to $\exp(-E_0^2/E^2)$, with the radiation electric field amplitude $E$ and the characteristic field parameter $E_0$. As observed in experiment, it exhibits a strong frequency dependence for $\omega \tau \gg 1$ characterized by the characteristic field $E_0$ linearly increasing with the radiation frequency $\omega$

Full Crystallographic Imaging of Hexagonal Boron Nitride Monolayers with Phonon-Enhanced Sum-Frequency Microscopy

Hexagonal boron nitride (hBN) is an important 2D material for van der Waals heterostructures, single photon emitters, and infrared nanophotonics. The optical characterization of mono- and few-layer samples of hBN however remains a challenge as the material is almost invisible optically. Here we introduce phase-resolved sum-frequency microscopy as a technique for imaging monolayers of hBN grown by chemical vapor deposition (CVD) and visualize their crystal orientation. A combination of femtosecond mid-infrared (IR) and visible laser pulses is used for sum-frequency generation (SFG), which is imaged in a wide-field optical microscope. The IR laser resonantly excites a phonon of hBN that leads to an ~800-fold enhancement of the SFG intensity, making it possible to image large 100x100 µm2 sample areas in less than 1 s. Implementing heterodyne detection in combination with azimuthal rotation of the sample further provides full crystallographic information. Through combined knowledge of topography and crystal orientation, we find that triangular domains of CVD-grown monolayer hBN have nitrogen-terminated zigzag edges. Overall, SFG microscopy can be used as an ultra-sensitive tool to image crystal structure, strain, stacking sequences, and twist angles, and is applicable to the wide range of van der Waals structures, where location and identification of monolayer regions and interfaces with broken inversion symmetry is of paramount importance

The efficacy of islet autoantibody screening with or without genetic pre-screening strategies for the identification of presymptomatic type 1 diabetes

Early detection of type 1 diabetes, in its presymptomatic stage, offers significant clinical advantages, including treatment that can delay disease onset. Current screening focuses on identifying islet autoantibody positivity, with proposed optimal testing at ages 2, 6 and 10 years potentially achieving up to 80% sensitivity. However, challenges arise from participation rates and costs associated with multiple screenings. Genetic pre-screening has been suggested as a complementary strategy to target high-risk individuals prior to autoantibody testing, but its real-world benefits remain uncertain. Broad genetic selection strategies, based on family history, HLA typing or polygenic risk scores, can identify subsets of the population at elevated risk. However, these approaches face issues like low recall rates, socioeconomic biases and limited applicability across diverse ancestries. Additionally, the cost-effectiveness and infrastructure requirements of integrating genetic testing into routine healthcare remain significant hurdles. The combined use of genetic and autoantibody testing could improve predictive value, especially with innovations like point-of-care genetic testing. Yet, the ultimate success of any screening programme depends less on specific strategies and more on maximising public and healthcare-provider engagement, ensuring high participation, and addressing socioeconomic and demographic disparities. Digital-health infrastructure may play a crucial role in improving recall rates and maintaining follow-up adherence. In conclusion, while repeated islet autoantibody screening remains the most effective standalone approach, conducting genetic screening prior to islet autoantibody testing may be practical in certain contexts, provided that sufficient resources and equitable strategies are employed. Public engagement and robust infrastructure are essential to realising the full potential of early type 1 diabetes detection programmes.</p

Building a Web-Based Knowledge Repository on Climate Change to Support Environmental Communities

This paper presents the technology base and roadmap of the Climate Change Collaboratory, a Web-based platform that aims to strengthen the relations between scientists, educators, environmental NGOs, policy makers, news media and corporations - stakeholders who recognize the need for adaptation and mitigation, but differ in world-views, goals and agendas. The collaboratory manages expert knowledge and provides a platform for effective communication and collaboration. It aims to assist networking with leading international organizations, bridges the science-policy gap and promotes rich, self-sustaining community interaction to translate knowledge into coordinated action. Innovative survey instruments in the tradition of "games with a purpose" will create shared meaning through collaborative ontology building and leverage social networking platforms to capture indicators of environmental attitudes, lifestyles and behaviors

Infrared photoresistance as a sensitive probe of electronic transport in twisted bilayer graphene

We report on observation of the infrared photoresistance of twisted bilayer graphene (tBLG) under continuous quantum cascade laser illumination at a frequency of 57.1 THz. The photoresistance shows an intricate sign alternating behavior under variations of temperature and back gate voltage, and exhibits giant resonance-like enhancements at certain gate voltages. The structure of the photoresponse correlates with weaker features in the dark dc resistance reflecting the complex band structure of tBLG. It is shown that the observed photoresistance is well captured by a bolometric model describing the electron and hole gas heating, which implies an ultrafast thermalization of the photoexcited electron–hole pairs in the whole range of studied temperatures and back gate voltages. We establish that photoresistance can serve a highly sensitive probe of the temperature variations of electronic transport in tBLG

Calorie restriction does not elicit a robust extension of replicative lifespan in Saccharomyces cerevisiae

Calorie restriction (CR) is often described as the most robust manner to extend lifespan in a large variety of organisms. Hence, considerable research effort is directed toward understanding the mechanisms underlying CR, especially in the yeast Saccharomyces cerevisiae. However, the effect of CR on lifespan has never been systematically reviewed in this organism. Here, we performed a meta-analysis of replicative lifespan (RLS) data published in more than 40 different papers. Our analysis revealed that there is significant variation in the reported RLS data, which appears to be mainly due to the low number of cells analyzed per experiment. Furthermore, we found that the RLS measured at 2% (wt/vol) glucose in CR experiments is partly biased toward shorter lifespans compared with identical lifespan measurements from other studies. Excluding the 2% (wt/vol) glucose experiments from CR experiments, we determined that the average RLS of the yeast strains BY4741 and BY4742 is 25.9 buds at 2% (wt/vol) glucose and 30.2 buds under CR conditions. RLS measurements with a microfluidic dissection platform produced identical RLS data at 2% (wt/vol) glucose. However, CR conditions did not induce lifespan extension. As we excluded obvious methodological differences, such as temperature and medium, as causes, we conclude that subtle method-specific factors are crucial to induce lifespan extension under CR conditions in S. cerevisiae

Clinical outcomes of pediatric kidney replacement therapy after childhood cancer—An ESPN/ERA Registry study

Cancer and its treatment may lead to kidney injury and the need for kidney replacement therapy (KRT). We identified 287 pediatric KRT patients with a history of malignancy from the European Society for Paediatric Nephrology/European Renal Association Registry. Of these, 197 had cancer as a primary cause of KRT (group 1) and 90 had a malignancy diagnosis before KRT (group 2). Two matched controls without malignancy were randomly selected for each patient. Data were complemented with a questionnaire. Median time to kidney transplantation (KT) from KRT initiation was 2.4 (IQR: 1.5-4.7), 1.5 (IQR: 0.4-3.3), 3.6 (IQR: 1.3 to Q3 not reached), and 1.1 (IQR: 0.3-3.6) years for group 1, their controls, group 2, and their controls, respectively. Overall 10-year mortality for those on KRT was higher among cancer patients vs controls in group 1: 16% vs 9% (adjusted hazard ratio 2.02, 95% CI: 1.21-3.37) and in group 2: 23% vs 14% (adjusted hazard ratio 2.32, 95% CI: 1.11-4.85). In contrast, 10-year patient survival after the first KT was comparable to controls (93% vs 96%; 100% vs 94%, in groups 1 and 2, respectively). In summary, childhood cancer survivors’ KT was delayed, and their overall mortality when on KRT was increased, but once transplanted, their long-term outcome was similar to other KT recipients

Disparities in treatment and outcome of kidney replacement therapy in children with comorbidities: an ESPN/ERA Registry study

Background Data on comorbidities in children on kidney replacement therapy (KRT) are scarce. Considering their high relevance for prognosis and treatment, this study aims to analyse the prevalence and implications of comorbidities in European children on KRT. Methods We included data from patients <20 years of age when commencing KRT from 2007 to 2017 from 22 European countries within the European Society of Paediatric Nephrology/European Renal Association Registry. Differences between patients with and without comorbidities in access to kidney transplantation (KT) and patient and graft survival were estimated using Cox regression. Results Comorbidities were present in 33% of the 4127 children commencing KRT and the prevalence has steadily increased by 5% annually since 2007. Comorbidities were most frequent in high-income countries (43% versus 24% in low-income countries and 33% in middle-income countries). Patients with comorbidities had a lower access to transplantation {adjusted hazard ratio [aHR] 0.67 [95% confidence interval (CI) 0.61-0.74]} and a higher risk of death [aHR 1.79 (95% CI 1.38-2.32)]. The increased mortality was only seen in dialysis patients [aHR 1.60 (95% CI 1.21-2.13)], and not after KT. For both outcomes, the impact of comorbidities was stronger in low-income countries. Graft survival was not affected by the presence of comorbidities [aHR for 5-year graft failure 1.18 (95% CI 0.84-1.65)]. Conclusions Comorbidities have become more frequent in children on KRT and reduce their access to transplantation and survival, especially when remaining on dialysis. KT should be considered as an option in all paediatric KRT patients and efforts should be made to identify modifiable barriers to KT for children with comorbidities.Lay Summary Kidney transplantation (KT) is considered the optimal treatment for children who suffer from permanent kidney failure, because it leads to a lower mortality and higher quality of life compared with dialysis. Children on dialysis frequently suffer from diseases of other organs (comorbidities) that can directly lower their life expectancy and could potentially represent a barrier for transplantation, posing an additional disease burden for these children. In this study we looked at data from a large multinational registry for children with kidney failure who require kidney replacement. Using these data, we studied whether these children suffered from comorbidities and whether these impact their life expectancy or their access to KT. We found that more and more children with kidney failure suffer from comorbidities when starting kidney replacement therapy. We also found that these children have a lower access to KT and a higher mortality on dialysis compared with children without comorbidities, especially in low-income countries. After KT, children with comorbidities have a similar mortality and graft survival compared with children without comorbidities. We concluded that reduced access to a kidney transplant might represent a modifiable barrier to KT in children with comorbidities, especially in low-resource countries. We suggest that children with comorbidities in need for kidney replacement therapy should be rapidly evaluated for eligibility for KT