Lead chalcogenides have long been used for space‐based and thermoelectric remote power generation applications, but recent discoveries have revealed a much greater potential for these materials. This ...renaissance of interest combined with the need for increased energy efficiency has led to active consideration of thermoelectrics for practical waste heat recovery systems—such as the conversion of car exhaust heat into electricity. The simple high symmetry NaCl‐type cubic structure, leads to several properties desirable for thermoelectricity, such as high valley degeneracy for high electrical conductivity and phonon anharmonicity for low thermal conductivity. The rich capabilities for both band structure and microstructure engineering enable a variety of approaches for achieving high thermoelectric performance in lead chalcogenides. This Review focuses on manipulation of the electronic and atomic structural features which makes up the thermoelectric quality factor. While these strategies are well demonstrated in lead chalcogenides, the principles used are equally applicable to most good thermoelectric materials that could enable improvement of thermoelectric devices from niche applications into the mainstream of energy technologies.
Band structure engineering approaches for high‐performance thermoelectric materials have been demonstrated in lead chalcogenides, shedding light on effective strategies to increase the performance of thermoelectrics. These approaches for enhancing electrical properties are in principle independent of other mechanisms to achieve low lattice thermal conductivity, and enable a combination of effects for revolutionary applications of thermoelectrics.
OPTN/SRTR 2018 Annual Data Report: Kidney Hart, A.; Smith, J. M.; Skeans, M. A. ...
American journal of transplantation,
January 2020, 2020-01-00, 20200101, Letnik:
20, Številka:
s1
Journal Article
Recenzirano
Odprti dostop
Despite the ongoing severe mismatch between organ need and supply, data from 2018 revealed some promising trends. For the fourth year in a row, the number of patients waiting for a kidney transplant ...in the US declined and numbers of both deceased and living donor kidney transplants increased. These encouraging trends are tempered by ongoing challenges, such as a large proportion of listed patients with dialysis time longer than 5 years. The proportion of candidates aged 65 years or older continued to rise, and the proportion undergoing transplant within 5 years of listing continued to vary dramatically nationwide, from 10% to nearly 80% across donation service areas. Increasing trends in the recovery of organs from hepatitis C positive donors and donors with anoxic brain injury warrant ongoing monitoring, as does the ongoing discard of nearly 20% of recovered organs. While the number of living donor transplants increased, racial disparities persisted in the proportion of living versus deceased donors. Strikingly, the total number of kidney transplant recipients alive with a functioning graft is on track to pass 250,000 in the next 1‐2 years. The total number of pediatric kidney transplants remained steady at 756 in 2018. Deeply concerning to the pediatric community is the persistently low level of living donor kidney transplants, representing only 36.2% in 2018.
OPTN/SRTR 2020 Annual Data Report: Kidney Lentine, K. L.; Smith, J. M.; Hart, A. ...
American journal of transplantation,
March 2022, 2022-03-00, 20220301, Letnik:
22, Številka:
S2
Journal Article
Recenzirano
The year 2020 presented significant challenges to the field of kidney transplantation. After increasing each year since 2015 and reaching the highest annual count to date in 2019, the total number of ...kidney trans‐ plants decreased slightly, to 23642, in 2020. The decrease in total kidney transplants was due to a decrease in living donor transplants; the number of deceased donor transplants rose in 2020. The number of patients waiting for a kidney transplant in the United States declined slightly in 2020, driven by a slight drop in the number of new candidates added in 2020 and an increase in patients removed from the waiting list owing to death‐important patterns that correlated with the COVID‐19 pandemic. The complexities of the pandemic were accompanied by other ongoing challenges. Nationwide, only about a quarter of waitlisted patients receive a deceased donor kidney transplant within 5 years, a proportion that varies dramatically by donation service area, from 14.8% to 73.0%. The nonutilization (discard) rate of recovered organs rose to its highest value, at 21.3%, despite a dramatic decline in the discard of organs from hepatitis C‐positive donors. Nonutilization rates remain particularly high for Kidney Donor Profile Index ≥85% kidneys and kidneys from which a biopsy specimen was obtained. Due to pandemic‐related disruption of living donation in spring 2020, the number of living donor transplants in 2020 declined below annual counts over the last decade. In this context, only a small proportion of the waiting list receives living donor transplants each year, and racial disparities in living donor transplant access persist. As both graft and patient survival continue to improve incrementally, the total number of living kidney transplant recipients with a functioning graft exceeded 250,000 in 2020. Pediatric transplant numbers seem to have been impacted by the COVID‐19 pandemic. The total number of pediatric kidney transplants performed decreased to 715 in 2020, from a peak of 872 in 2009. Despite numerous efforts, living donor kidney transplant remains low among pediatric recipients, with continued racial disparities among recipients. Of concern, the rate of deceased donor transplant among pediatric waitlisted candidates continued to decrease, reaching its lowest point in 2020. While this may be partly explained by the COVID‐19 pandemic, close attention to this trend is critically important. Congenital anomalies of the kidney and urinary tract remain the leading cause of kidney disease in the pediatric population. While most pediatric de‐ ceased donor recipients receive a kidney from a donor with KDPI less than 35%, most pediatric deceased donor recipients had four or more HLA mis‐ matches. Graft survival continues to improve, with superior survival for living donor recipients versus deceased donor recipients.
OPTN/SRTR 2019 Annual Data Report: Kidney Hart, A.; Lentine, K. L.; Smith, J. M. ...
American journal of transplantation,
February 2021, 2021-02-00, 20210201, Letnik:
21, Številka:
S2
Journal Article
Recenzirano
Odprti dostop
Despite the ongoing severe shortage of available kidney grafts relative to candidates in need, data from 2019 reveal some promising trends. After remaining relatively stagnant for many years, the ...number of kidney transplants has increased each year since 2015, reaching the highest annual count to date of 24,273 in 2019. The number of patients waiting for a kidney transplant in the United States was relatively stable, despite an increase in the number of new candidates added in 2019 and a decrease in patients removed from the waiting list owing to death or deteriorating medical condition. However, these encouraging trends are tempered by ongoing challenges. Nationwide, only a quarter of waitlisted patients receive a deceased‐donor kidney transplant within 5 years, and this proportion varies dramatically by donation service area, from 15.5% to 67.8%. The non‐utilization (discard) rate of recovered organs remains at 20.1%, despite adramatic decline in the discard of organs from hepatitis C‐positive donors. Non‐utilization rates remain particularly high for Kidney Donor Profile Index ≥85% kidneys and kidneys from which a biopsy specimen was obtained. While the number of living‐donor transplants increased again in 2019, only a small proportion of the waiting list receives living‐donor transplants each year, and racial disparities in living‐donor transplant access persist. As both graft and patient survival continue to improve incrementally, the total number of living kidney transplant recipients with a functioning graft is anticipated to exceed 250,000 in the next 1‐2 years. Over the past decade, the total number of pediatric kidney transplants performed has remained stable. Despite numerous efforts, living donor kidney transplant remains low among pediatric recipients with continued racial disparities among recipients. Congenital anomalies of the kidney and urinary tract remain the leading cause of kidney disease. While most deceased donor recipients receive a kidney from a donor with KDPI less than 35%, the majority of pediatric recipients had four or more HLA mismatches. Graft survival continues to improve with superior outcomes for living donor recipients.
Objective
To describe differences in outcomes between pregnant women with and without coronavirus dsease 2019 (COVID‐19).
Design
Prospective cohort study of pregnant women consecutively admitted for ...delivery, and universally tested via nasopharyngeal (NP) swab for severe acute respiratory syndrome coronavirus 2 (SARS‐CoV‐2) using reverse transcription–polymerase chain reaction. All infants of mothers with COVID‐19 underwent SARS‐CoV‐2 testing.
Setting
Three New York City hospitals.
Population
Pregnant women >20 weeks of gestation admitted for delivery.
Methods
Data were stratified by SARS‐CoV‐2 result and symptomatic status, and were summarised using parametric and nonparametric tests.
Main outcome measures
Prevalence and outcomes of maternal COVID‐19, obstetric outcomes, neonatal SARS‐CoV‐2, placental pathology.
Results
Of 675 women admitted for delivery, 10.4% were positive for SARS‐CoV‐2, of whom 78.6% were asymptomatic. We observed differences in sociodemographics and comorbidities among women with symptomatic COVID‐10 versus asymptomatic COVID‐19 versus no COVID‐19. Caesarean delivery rates were 46.7% in symptomatic COVID‐19, 45.5% in asymptomatic COVID‐19 and 30.9% in women without COVID‐19 (P = 0.044). Postpartum complications (fever, hypoxia, readmission) occurred in 12.9% of women with COVID‐19 versus 4.5% of women without COVID‐19 (P < 0.001). No woman required mechanical ventilation, and no maternal deaths occurred. Among 71 infants tested, none were positive for SARS‐CoV‐2. Placental pathology demonstrated increased frequency of fetal vascular malperfusion, indicative of thrombi in fetal vessels, in women with COVID‐19 versus women without COVID‐19 (48.3% versus 11.3%, P < 0.001).
Conclusion
Among pregnant women with COVID‐19 at delivery, we observed increased caesarean delivery rates and increased frequency of maternal complications in the postpartum period. Additionally, intraplacental thrombi may have maternal and fetal implications for COVID‐19 remote from delivery.
Tweetable
COVID‐19 at delivery: more caesarean deliveries, postpartum complications and intraplacental thrombi.
Tweetable
COVID‐19 at delivery: more caesarean deliveries, postpartum complications and intraplacental thrombi.
This article includes Author Insights, a video available at https://vimeo.com/rcog/authorinsights16403
The improvement of catalysts for the four-electron oxygen-reduction reaction (ORR; O2+4H++4e−→2H2O) remains a critical challenge for fuel cells and other electrochemical-energy technologies. Recent ...attention in this area has centred on the development of metal alloys with nanostructured compositional gradients (for example, core–shell structure) that exhibit higher activity than supported Pt nanoparticles (Pt–C; refs 1,2,3,4,5,6,7). For instance, with a Pt outer surface and Ni-rich second atomic layer, Pt3Ni(111) is one of the most active surfaces for the ORR (ref. 8), owing to a shift in the d-band centre of the surface Pt atoms that results in a weakened interaction between Pt and intermediate oxide species, freeing more active sites for O2 adsorption. However, enhancements due solely to alloy structure and composition may not be sufficient to reduce the mass activity enough to satisfy the requirements for fuel-cell commercialization, especially as the high activity of particular crystal surface facets may not easily translate to polyfaceted particles. Here we show that a tailored geometric and chemical materials architecture can further improve ORR catalysis by demonstrating that a composite nanoporous Ni–Pt alloy impregnated with a hydrophobic, high-oxygen-solubility and protic ionic liquid has extremely high mass activity. The results are consistent with an engineered chemical bias within a catalytically active nanoporous framework that pushes the ORR towards completion.
OPTN/SRTR 2020 Annual Data Report: Liver Kwong, A. J.; Ebel, N. H.; Kim, W. R. ...
American journal of transplantation,
March 2022, 2022-03-00, 20220301, Letnik:
22, Številka:
S2
Journal Article
Recenzirano
This year was marked by the COVID‐19 pandemic, which altered transplant program activity and affected waitlist and transplant outcomes. Still, 8906 liver transplants were performed, an all‐time high, ...across 142 centers in the United States, and pretransplant as well as graft and patient survival metrics, continued to improve. Living donation activity decreased after several years of growth. As of June 30, 2020, 98989 liver transplant recipients were alive with a functioning graft, and in the context of increasing liver transplant volume, the size of both the adult and pediatric liver transplant waitlists have decreased. On February 4, 2020, shortly before the pandemic began, a new liver distribution policy based on acuity circles was implemented, replacing donor service area‐ and region‐based boundaries. A policy change to direct pediatric livers to pediatric recipients led to an increase in deceased donor transplant rates and a decrease in pretransplant mortality rate among children, although the absolute number of pediatric transplants did not increase in 2020. Among adults, alcohol‐associated liver disease became the predominant indication for liver transplant in 2020. After implementation of the National Liver Review Board and lower waitlist priority for most exception cases in 2019, fewer liver transplants were being performed via exception points, and the transplant rate between those with and without hepatocellular carcinoma has equalized. Women continue to experience higher pretransplant mortality and lower rates of liver transplant than men.
OPTN/SRTR 2019 Annual Data Report: Liver Kwong, A. J.; Kim, W. R.; Lake, J. R. ...
American journal of transplantation,
February 2021, 2021-02-00, 20210201, Letnik:
21, Številka:
S2
Journal Article
Recenzirano
Odprti dostop
This year was notable for changes to exception points determined by the geographic median allocation Model for End‐Stage Liver Disease (MELD) and implementation of the National Liver Review Board, ...which took place on May 14, 2019. The national acuity circle liver distribution policy was also implemented but reverted to donor service area‐ and region‐based boundaries after 1 week. In 2019, growth continued in the number of new waiting list registrations (12,767) and transplants performed (8,896), including living‐donor transplants (524). Compared with 2018, living‐donor liver transplants increased 31%. Women continued to have a lower deceaseddonor transplant rate and a higher pretransplant mortality rate than men. The median waiting time for candidates with a MELD of 15‐34 decreased, while the number of transplants performed for patients with exception points decreased. These changes may have been related to the policy changes that took effect in May 2019, which increased waiting list priority for candidates without exception status. Hepatitis C continued to decline as an indication for liver transplant, as the proportion of liver transplant recipients with alcohol‐related liver disease and clinical profiles consistent with non‐alcoholic steatohepatitis increased. Graft and patient survival have improved despite changing recipient demographics including older age, higher MELD, and higher prevalence of obesity and diabetes.
Satellite survey is widely used for archaeological site discovery, but the efficacy of the method has received little systematic investigation. In this analysis, twelve study participants of ...different experience levels performed an unstructured remote survey of 197 km2 in the Sama and Moquegua valleys of south central Peru where previous pedestrian surveys recorded 546 archaeological sites. Results indicate an average site discovery rate of 9.3% (0-18%, 95% range). The most experienced participants detect up to 20% (17-22%) of known archaeological sites. These detection rates can be used to derive reliable site frequency estimates on the Andean coast, which can be used in planning and budgeting for field efforts and estimating demographic patterns at large spatial scales that are difficult to achieve through pedestrian survey. More generally, this analysis offers a method for deriving correction terms specific to other parts of the world. Additionally, the results can serve as a baseline for evaluating the effectiveness of emerging artificial intelligence routines for archaeological site detection.
OPTN/SRTR 2016 Annual Data Report: Kidney Hart, A.; Smith, J. M.; Skeans, M. A. ...
American journal of transplantation,
January 2018, 2018-01-00, 20180101, Letnik:
18, Številka:
S1
Journal Article
Recenzirano
Odprti dostop
Data from 2016 show ongoing positive trends in short‐ and long‐term allograft survival, and a decrease in the number of active listed candi‐ dates for the first time in more than a decade, with a ...concomitant in‐ crease in deceased donor kidney transplants. Transplant rates that had changed dramatically for some groups after implementation of the new kidney allocation system in 2014 are stabilizing, allowing for evaluation of new steady states and trends. Many challenges remain in adult kid‐ ney transplantation, including stagnant rates of living donor transplant, geographic disparities in access to transplant, racial disparities in living donor transplant, and overall a continuing demand for kidneys that far outpaces the supply. For pediatric recipients, a decline in the proportion of living donor transplants is of concern. In 2016, only 34.2% of pediatric transplants were from living donors, compared with 47.2% in 2005. The number of related donors decreased dramatically over the past decade, and the number of unrelated directed transplants performed in pediatric candidates remained low (50).
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