Search

The negative impact of COVID-19 on adults with underlying chronic kidney disease, including kidney transplant recipients, has been well documented. Children have a less severe presentation and better prognosis compared to adults. However, little is known regarding the spectrum of COVID-19 infection in children and adolescents with underlying autoimmune disorders necessitating solid organ transplant and long-term immunosuppressive therapy. Case Report. An adolescent male developed end-stage kidney disease secondary to microscopic polyangiitis requiring a living-donor kidney transplant. Six years later, he developed antibody-mediated rejection of his kidney transplant. During his rejection treatment course, he contracted SARS-CoV-2 and developed new-onset nephrotic syndrome with severe acute kidney injury. Kidney transplant biopsy revealed de novo collapsing focal segmental glomerulosclerosis on a background of chronic active antibody mediated rejection. Immunostaining for SARS-CoV-2 on the biopsy specimen demonstrated positive staining of the proximal tubular epithelium consistent with intra-renal viral infection. Pulse corticosteroids, intravenous immunoglobulin, and temporary reduction of anti-metabolite therapy resulted in successful recovery with return of graft function back to pre-infection baseline. This case highlights the clinical conundrum of treating kidney transplant recipients with active rejection in the midst of the COVID-19 pandemic. Pediatric kidney transplant recipients can develop severe COVID-19-related kidney complications. Judicious immunosuppression modulation is necessary to balance infection and rejection risk.

Surface-enhanced Raman spectroscopy (SERS) technology is an attractive method for the prompt and accurate on-site screening of illicit drugs. As portable Raman systems are available for on-site screening, the readiness of SERS technology for sensing applications is predominantly dependent on the accuracy, stability and cost-effectiveness of the SERS strip. An atmospheric-pressure plasma-assisted chemical deposition process that can deposit an even distribution of nanogold particles in a one-step process has been developed. The process was used to print a nanogold film on a paper-based substrate using a HAuCl4 solution precursor. X-ray photoelectron spectroscopy (XPS) analysis demonstrates that the gold has been fully reduced and that subsequent plasma post-treatment decreases the carbon content of the film. Results for cocaine detection using this substrate were compared with two commercial SERS substrates, one based on nanogold on paper and the currently available best commercial SERS substrate based on an Ag pillar structure. A larger number of bands associated with cocaine was detected using the plasma-printed substrate than the commercial substrates across a range of cocaine concentrations from 1 to 5000 ng/mL. A detection limit as low as 1 ng/mL cocaine with high spatial uniformity was demonstrated with the plasma-printed substrate. It is shown that the plasma-printed substrate can be produced at a much lower cost than the price of the commercial substrate.

Runaway electron generation remains one of the major challenges to the success of high-current tokamaks. Investigation of runaway electron physics is a crucial step towards developing effective prediction, avoidance, and mitigation strategies to reduce the impact of these dangerous events. Valuable information on the runaway electron distribution function can be obtained performing spectral analysis of the bremsstrahlung radiation emitted in the interaction between the runaway beam and the post-disruption plasma. Measurement of this radiation is challenging and requires dedicated instruments. This work presents REGARDS, a novel portable hard X-ray spectrometer optimised for bremsstrahlung radiation measurement from runaway electrons in fusion plasmas. The detector is based on a 1"x1" LaBr3:Ce scintillator crystal coupled with a photomultiplier tube. The system has an energy range exceeding 20 MeV with an energy resolution of 3% at 661.7 keV. The detector gain is stable even under severe HXR flux (gain shift below 3% with a HXR counting rate in excess of 1 MCps). The high performance of the system enables unprecedented studies of the time-dependent runaway electron energy distribution function. Examples from recent runaway electron physics experiments performed at the ASDEX Upgrade and COMPASS tokamaks are shown.

Infectious complications are currently the most common cause of hospitalization post-kidney transplantation. Urinary tract infections (UTIs) are the most common infectious complication post-kidney transplant in children and are particularly frequent in those with underlying congenital anomalies of the kidneys and urinary tract (CAKUT). Long-term immunosuppression predisposes to opportunistic infections including cytomegalovirus (CMV), Epstein-Barr virus (EBV), BK polyoma virus, and Pneumocystis jirovecii pneumonia (PJP) infections. Most transplant centers screen for these infections utilizing high-sensitivity polymerase chain reaction (PCR) assays at routine intervals post-transplantation. Effective anti-viral therapies are available for CMV infection, whereas reduction of immunosuppression remains the mainstay of managing EBV and BK polyoma virus infections. Uncontrolled EBV replication post-transplant has been associated with post-transplant lymphoproliferative disorder (PTLD). Other cancer types, particularly skin cancer, are seen at higher frequencies post-kidney transplantation with longer duration and intensity of immunosuppression. A thorough understanding of the risk factors predisposing to these complications is critical to prevent their occurrences and limit recipient morbidity and mortality.

The patient is a 3-month-old male with known, mild, right-sided hydronephrosis secondary to ureteropelvic junction obstruction (UPJO), who presented to the emergency department with 1 week of poor feeding, episodic emesis, and abdominal distension. The family denied any change in urine output, but did affirm apparent discomfort when stooling, irritability, and grunting. In the emergency department, BP was 140/79 mm Hg in the right upper extremity. Laboratory workup was unremarkable: specifically, urinalysis was found to be free of blood and protein, with only 1+ leukocyte esterase and normal kidney function. Abdominal ultrasound revealed massive pelvocaliectasis of the right kidney, with the kidney parenchyma stretched and thinned over the massively dilated central collecting system (Figure 1). Findings were confirmed on the abdominal computed tomography scan, which also revealed the profound mass effect on the abdominal organs, vessels, and bowel, specifically compressing and displacing the …

BACKGROUND: Nephrotic syndrome (NS) results in hypercoagulability and increased risk of infection. Furthermore, infection increases the risk of venous thromboembolism (VTE). Our objective was to determine the prevalence of infection, VTE, and the associated outcomes among a cohort of hospitalized children with NS. METHODS: All children with NS admitted to 17 pediatric hospitals across North America from 2010 to 2012 were included. Prevalence of infection and VTE was determined. Wilcoxon rank-sum and logistic regression were performed. RESULTS: Seven-hundred thirty hospitalizations occurred among 370 children with NS. One-hundred forty-eight children (40%) had ≥ 1 infection (211 episodes) and 11 (3%) had VTE. Those with VTE had infection more frequently (p = 0.046) and were younger at NS diagnosis (3.0 vs. 4.0 years; p = 0.008). The most common infectious pathogen identified was Streptococcus pneumoniae. The median hospital length of stay for those with infection [10 vs 5 days (p < 0.0001)] or VTE [22 vs 6 days (p < 0.0001)] was longer than those without either complication. Of those with infection, 13% had an intensive care unit (ICU) stay compared with 3.3% of those without infection. Median ICU stay was 4 days in those with VTE compared to 0 days in those without (p < 0.001). By logistic regression, only the number of ICU days was associated with VTE (OR 1.074, 95% CI 1.013–1.138). CONCLUSIONS: Hospitalized children with NS have high rates of infection. Presence of VTE was associated with infection. Both were associated with longer hospitalizations and ICU stays.

The epitaxial growth of lattice-mismatched semiconductors on silicon has attracted widespread attention for the possibility to exploit superior optical/transport properties of the deposited materials while maintaining compatibility with mainstream Si technology. However, due to the lattice mismatch, elastic energy is accumulated in the deposited film up to a certain critical thickness, beyond which plastic relaxation sets in. The latter can be conveniently controlled by growing graded layers. Such substrates proved to be extremely appealing in terms of reducing the threading-dislocation density (TDD) down to values of the order of 10^6 cm-2. The remarkable reduction of the TDD is of particular importance since those defects have detrimental impacts on the properties of integrated devices. However, continuous shrinking of the devices dimensions calls for a further decrease in the TDD, as even a single defect could be sufficient to severely alter the desired functionality. To address this problem, complex techniques deviating from the standard planar film geometry and aimed at producing dislocation-free materials in selected active areas have been developed, such as 3D heteroepitaxy [2]. This requires the deposition of Ge (or SiGe) onto an ordered array of micrometric, square Si pillars. The combined effect of strong out-of-equilibrium growth conditions and mutual shadowing among neighbouring pillars, leads to the formation of Vertical Heterostructures (VHE), whose upper region can be fully dislocation-free. By combining the 3D heteroepitaxy approach with compositional grading, 100% dislocation-free SiGe crystals were recently demonstrated [3]. Properly grading the layer in VHE allows to release completely the lattice-mismatch strain only by exploiting lateral elastic relaxation. As a result, neither misfit dislocations nor TDs, are introduced. Graded VHEs, however, still need further optimization before being easily exploited in applications. Indeed, 100% dislocation-free crystals can be obtained only by a proper choice of the growth parameters. Narrow crystals, and shallow compositional grading rate, favor the elastic stress relaxation mechanism. The aim of this work is to improve the design of these VHEs by suitably tuning the substrate geometry. Promising results in terms of the reduction of TDD inside the upper active area of the heterostructures are experimentally demonstrated, together with a theoretical interpretation of the main mechanism leading to the observed different distributions of dislocations. 2. Experimental results The experimental characterization was performed on SiGe VHEs grown on two different substrate geometries, one is the standard vertical Si pillar, while the other is an under-etched geometry [4] where the sidewalls of the Si pillars were subjected to an additional isotropic etching step as shown in Fig. 1. Fig. 1. SEM view showing the substrate geometries considered in this work. The standard vertical pillars (a) show dislocations mostly on the upper SiGe film, while for the under-etched Si pillar (b), the dislocations tend to dig into the substrate, piling up along the same {111} glide plane. We looked at the dislocation density (DD) for both cases, by counting the etch-pits extending up to the lateral free surfaces, both in the upper SiGe crystal and both inside the Si substrate underneath. The results [5] show that the dislocation density for the upper part, DDSiGe, is lower in the under-etched case with respect to the vertical one, for all the pillar bases considered. By contrast, the dislocation density in the substrate, DDSi, increases for the under-etched case. 3. Model and comparisons The approach exploited in this work to model the experimental distributions of dislocations is a coupling between a two-dimensional dislocation dynamics code and a Finite Element (FE) solver, in the isotropic linear elasticity framework. The coupling is based on the eigenstrain formalism, implemented following the Discrete-Continuous Model presented in Ref. [6]. In this approach, the motion of dislocations follows the Peach-Koehler force. where is the stress field at the dislocation position obtained by the FE solution, its Burgers vector and the dislocation line. Fig. 2. Energy gain for the introduction of a ‘normal’ (red dashed line) and an ‘opposite’ (blue solid line) dislocation plotted against the thickness of the deposited SiGe crystal. The coupling with the FE solver permitted us to evaluate also the total elastic energy in the system and thus to provide a thermodynamical prediction for the onset of plasticity. This was achieved by probing different positions for the insertion of the dislocation in the system and by taking the energy difference between the configurations with and without the defect. The results, as shown in Fig. 2, demonstrate that, for the under-etched geometry, the kind of defects introduced has the opposite sign of the Burgers vector with respect to dislocations normally introduced in SiGe/Si heteroepitaxy (here named ‘normal’ dislocations). This difference with respect to the vertical geometry for the Si pillars helps to explain the different distribution of dislocations found experimentally. In fact, dislocation dynamics simulations performed on pile-ups of identical dislocations aligned along the same {111} glide plane predicts a different behavior for the two investigated geometries, as reported in Fig. 3. The comparison with the experimental results of Fig. 1 shows a nice qualitative agreement: for the vertical Si pillar the dislocations tend to be concentrated in the SiGe crystal while for the under-etched case the pile-ups are found inside the Si substrate, explaining in this way also the difference in the DD observed [5]. Fig. 3. Hydrostatic stress maps obtained from the final distribution of dislocations simulated by means of dislocation dynamics for the two investigated geometries: vertical Si pillar on the left and under-etched pillar on the right. A further analysis can be performed by looking at the typical number of dislocations per pile-up predicted theoretically by exploiting again an energetic criterion as described above. The results show [5] that a number of 4 dislocation per pile-up corresponds to the minimum energy configuration for our systems, in excellent agreement with the experimental distribution taken on a wide range of pillars, that shows a maximum probability of having a number between 3 and 4 dislocations per pile-up. 4. Conclusions In this work we have presented a combined theoretical and experimental investigation of dislocation distributions in graded SiGe crystals grown on vertical and under-etched Si pillars. As shown, the main role played by under-etching is to effectively invert the sign of the Burgers vectors of the dislocations. The modeling of the typical dislocation positioning leads to nice agreement with experiments both in terms of distribution and in number of defects [5]. This study opens the way for future research, e.g. on optimal shaping of the pillars, with the aim of growing larger dislocation-free SiGe crystals. References [1] E.A. Fitzgerald, Materials Science Report 7, 87 (1991). [2] C. Falub et al., Science 335, 1330 (2012). [3] F. Isa et al., Advanced Materials 28, 884 (2016). [4] F. Isa et al., Applied Physics Letters 109, 182112 (2016). [5] F. Rovaris, et al., Physical Review Material 1, 073602 (2017). [6] A. Jamond, et al., International Journal of Plasticity 80, 19 (2016)

Background Cardiovascular disease is a major cause of morbidity and mortality in children with chronic kidney disease. We sought to determine the prevalence of cardiovascular risk factors in children with glomerular disease and to describe current practice patterns regarding risk factor identification and management. Methods and Results Seven‐hundred sixty‐one children aged 0 to 17 years with any of 4 biopsy‐confirmed primary glomerular diseases (minimal change disease, focal segmental glomerulosclerosis, membranous nephropathy, and IgA nephropathy/vasculitis) were enrolled at a median of 16 months from glomerular disease diagnosis in the multicenter prospective Cure Glomerulonephropathy Network study. Prevalence of traditional (hypertension, hypercholesterolemia, and obesity) and novel (proteinuria, prematurity, and passive smoke exposure) cardiovascular risk factors were determined at enrollment and compared across glomerular disease subtypes. Frequency of screening for dyslipidemia and prescribing of lipid‐lowering or antihypertensive medications were compared across glomerular disease subtype, steroid exposure, and remission status groups. Compared with the general population, all traditional risk factors were more frequent: among those screened, 21% had hypertension, 51% were overweight or obese, and 71% had dyslipidemia. Children who were not in remission at enrollment were more likely to have hypertension and hypercholesterolemia. Fourteen percent of hypertensive children were not receiving antihypertensives. Only 49% underwent screening for dyslipidemia and only 9% of those with confirmed dyslipidemia received lipid‐lowering medications. Conclusions Children with primary glomerular diseases exhibit a high frequency of modifiable cardiovascular risk factors, particularly untreated dyslipidemia. Lipid panels should be routinely measured to better define the burden of dyslipidemia in this population. Current approaches to screening for and treating cardiovascular risk factors are not uniform, highlighting a need for evidence‐based, disease‐specific guidelines.

Minimally invasive surgical techniques including robotic-assisted laparoscopic ureteral reimplantation and endoscopic transurethral injection are becoming increasingly prevalent. They are associated with a high success rate, shorter hospital stay, and an excellent safety profile. This review contains 6 figures, 5 tables, 1 video, and 90 references. Key words: congenital reflux nephropathy, acquired reflux nephropathy, robotic-assisted laparoscopic ureteral reimplantation, reflux nephropathy, primary vesicoureteral reflux, urinary tract infection

Banff 2013 criteria recommend performing ultrastructural studies with electron microscopy (EM) in kidney transplant biopsies if the technology is available. We sought to determine the impact of EM on enhancing diagnostic findings in pediatric kidney transplant biopsies and the prognostic information gained from the additional findings. All kidney transplant biopsies since routine EM use started on June 1, 2014, until October 31, 2016, were reviewed. Primary outcome measures included the positive yield frequency of EM use defined as an upgraded diagnosis based on EM findings relative to light microscopy, and 12-month kidney allograft outcome of progression to ESRD or doubling of serum creatinine stratified by transplant glomerulopathy (TG) status on EM. Eighty unique kidney transplant biopsies were reviewed. EM studies were completed for 61 biopsies (76%). Complication rate was low (3.7%). In 61 biopsies where EM was completed, EM findings included foot process fusion (62%), endothelial cell swelling (38%), subendothelial lucencies (31%), and glomerular basement membrane duplication (41%). EM confirmed FSGS recurrence in three cases. In the remaining 58 cases, there was a positive yield of 31% where 18 biopsies were upgraded to a worse category after TG identification on EM. Kidney allograft outcome was poor regardless whether TG was detected early on EM or advanced on LM. Routine EM use in analyzing pediatric kidney transplant biopsies proved safe and provided valuable additional diagnostic information in almost one-third of cases. Additional studies are needed to determine if clinical interventions for early TG identified on EM can improve long-term outcomes.

West Nile Virus is an arbovirus that has rapidly spread throughout the United States since the first case was described in Queens, New York in 1999. There has been increasing reports of both community-acquired and organ-derived infections in renal transplant recipients. In immunocompromised individuals, WNV infection is a life-threatening disease with significant neurological morbidity. We report the only pediatric case of community-acquired WNV disease in a renal transplant recipient to undergo detailed long-term neuropsychological assessment. Increased surveillance and prompt treatment of WNV meningoencephalitis is critical, and our report highlights the effectiveness of immunosuppression reduction without compromising allograft outcomes.

Non-immunologic risk factors are a major obstacle to realizing long-term improvements in kidney allograft survival. A standardized approach to assess donor quality has recently been introduced with the new kidney allocation system in the USA. Delayed graft function and surgical complications are important risk factors for both short- and long-term graft loss. Disease recurrence in the allograft remains a major cause of graft loss in those who fail to respond to therapy. Complications of over immunosuppression including opportunistic infections and malignancy continue to limit graft survival. Alternative immunosuppression strategies are under investigation to limit calcineurin inhibitor toxicity. Finally, recent studies have confirmed long-standing observations of the significant negative impact of a high-risk age window in late adolescence and young adulthood on long-term allograft survival.

We wanted to identify practice patterns and perceived barriers among pediatric nephrologists regarding STI screening and reproductive health counseling in adolescent renal transplant recipients. We created an online Likert-scaled survey. Response rate was 54%. The majority (83%) believed STI risk in their patients was similar to or higher than healthy teens. Interestingly, while 67% felt moderately or very confident in asking about sexual activity and counseling about safer sex, only 43% routinely or always inquired about sexual activity, and only 42% routinely or always counseled about safer sex. Fifty-four percent routinely or always discussed contraceptive options and implications of unintentional pregnancy. Fifty-one percent routinely or always referred patients to a gynecologist or adolescent provider for contraception prescription. The most common counseling mechanism was informal discussions in clinic (87%). Ten percent had no mechanism in place. Major barriers included time limitations, adolescents' fear regarding confidentiality, and lack of professional training. This is the first report of perceptions and practice patterns of pediatric nephrologists regarding STI screening and reproductive health counseling. Providers seem to recognize the importance of counseling; however, translation into practice remains low. Professional training in this area and increased encounter time could improve counseling delivery and thereby reduce risk in this population.

Silicon offers a compelling platform for developing hybrid architectures that exploit novel functionalities. Heteroepitaxial growth of Ge on Si is a prominent approach to tailor material properties to achieve this goal. However, designing Ge-based heterostructures, which fulfill ever-demanding photonic and electronic applications, demands crucial control over the unavoidable non-radiative recombinations occurring at free surfaces and growth defects like dislocations. Yet the mitigation over such parasitic optical activity remains an open issue. Here we tackle this problem and demonstrate a more than 2 orders of magnitude photoluminescence (PL) enhancement achieved via confinement of threading dislocations and carefully controlled surface passivation of micron-scale Ge on Si crystals. By spectrally resolving interband and dislocation-related PL, we underpin the role played by dislocations in limiting the radiative emission, and we identify effective solutions based upon bandgap engineering to further boosting light emission efficiency. Noticeably, by combining steady state and time-resolved PL we disentangle non-radiative channels due to free surfaces and dislocations, eventually shining light on their relative impact at various temperature regimes. These findings have the potential of being beneficial for numerous applications of Ge-based heterostructures, in particular for moving forward their exploitation within the fast-growing field of Si-photonics.

Our work, focused on the heteroepitaxial Ge/Si (001) system shows that patterned Si substrates in appropriate pillar arrays, featuring micrometric dimensions within the common deep-etching capabilities and array size suitable for several applications (up to few hundreds microns), do provide exceptional compliance to the thermal strain of a continuous Ge film deposited on top. Micro-Raman and XRD measurements on the Ge suspended layer, as obtained by Low Energy Plasma Enhanced Chemical Vapor Deposition, confirm the theoretical predictions. Actually, the sharp onset with pillar aspect ratio of such an effect is demonstrated to be triggered by the free rotation of the pillars, as induced by the thermal contraction of the film. The strain relaxation is deeply analyzed both by FEM simulations and experimental XRD results, showing a very good quantitative agreement. Our findings have far reaching consequences beyond the crystalline heteroepitaxial systems, whenever a film of any microstructure, or composition, is deposited in suspended patches on suitable pillar arrays.

A summary of recent results on filamentary transport, mostly obtained in the ASDEX-Upgrade tokamak (AUG), is presented and discussed in an attempt to produce a coherent picture of SOL filamentary transport: A clear correlation is found between L-mode density shoulder formation in the outer midplane and a transition between the sheath limited and the inertial filamentary regimes. Divertor collisionality is found to be the parameter triggering the transition. A clear reduction of the ion temperature takes place in the far SOL after the transition, both for the background and the filaments. This coincides with a strong variation of the ion temperature distribution, which deviates from Gaussianity and becomes dominated by a strong peak below $5$ eV. The filament transition mechanism triggered by a critical value of collisionality seems to be generally applicable to inter-ELM H-mode plasmas, although a secondary threshold related to deuterium fueling is observed. EMC3-EIRENE simulations of neutral dynamics show that an ionization front near the main chamber wall is formed after the shoulder formation. Finally, a clear increase of SOL opacity to neutrals is observed associated to the shoulder formation. A common SOL transport framework is proposed account for all these results, and their potential implications for future generation devices are discussed., Published in Nuclear Fusion