A major goal of remote sensing is the development of generalizable algorithms to repeatedly and accurately map ecosystem properties across space and time. Imaging spectroscopy has great potential to ...map vegetation traits that cannot be retrieved from broadband spectral data, but rarely have such methods been tested across broad regions. Here we illustrate a general approach for estimating key foliar chemical and morphological traits through space and time using NASA's Airborne Visible/Infrared Imaging Spectrometer (AVIRIS-Classic). We apply partial least squares regression (PLSR) to data from 237 field plots within 51 images acquired between 2008 and 2011. Using a series of 500 randomized 50/50 subsets of the original data, we generated spatially explicit maps of seven traits (leaf mass per area (
M
area
), percentage nitrogen, carbon, fiber, lignin, and cellulose, and isotopic nitrogen concentration, δ
15
N) as well as pixel-wise uncertainties in their estimates based on error propagation in the analytical methods. Both
M
area
and %N PLSR models had a
R
2
> 0.85. Root mean square errors (RMSEs) for both variables were less than 9% of the range of data. Fiber and lignin were predicted with
R
2
> 0.65 and carbon and cellulose with
R
2
> 0.45. Although
R
2
of %C and cellulose were lower than
M
area
and %N, the measured variability of these constituents (especially %C) was also lower, and their RMSE values were beneath 12% of the range in overall variability. Model performance for δ
15
N was the lowest (
R
2
= 0.48, RMSE = 0.95‰), but within 15% of the observed range. The resulting maps of chemical and morphological traits, together with their overall uncertainties, represent a first-of-its-kind approach for examining the spatiotemporal patterns of forest functioning and nutrient cycling across a broad range of temperate and sub-boreal ecosystems. These results offer an alternative to categorical maps of functional or physiognomic types by providing non-discrete maps (i.e., on a continuum) of traits that define those functional types. A key contribution of this work is the ability to assign retrieval uncertainties by pixel, a requirement to enable assimilation of these data products into ecosystem modeling frameworks to constrain carbon and nutrient cycling projections.
The morphological and biochemical properties of plant canopies are strong predictors of photosynthetic capacity and nutrient cycling. Remote sensing research at the leaf and canopy scales has ...demonstrated the ability to characterize the biochemical status of vegetation canopies using reflectance spectroscopy, including at the leaf level and canopy level from air- and spaceborne imaging spectrometers. We developed a set of accurate and precise spectroscopic calibrations for the determination of leaf chemistry (contents of nitrogen, carbon, and fiber constituents), morphology (leaf mass per area,
M
area
), and isotopic composition (δ
15
N) of temperate and boreal tree species using spectra of dried and ground leaf material. The data set consisted of leaves from both broadleaf and needle-leaf conifer species and displayed a wide range in values, determined with standard analytical approaches: 0.7-4.4% for nitrogen (
N
mass
), 42-54% for carbon (
C
mass
), 17-58% for fiber (acid-digestible fiber, ADF), 7-44% for lignin (acid-digestible lignin, ADL), 3-31% for cellulose, 17-265 g/m
2
for
M
area
, and −9.4‰ to 0.8‰ for δ
15
N. The calibrations were developed using a partial least-squares regression (PLSR) modeling approach combined with a novel uncertainty analysis. Our PLSR models yielded model calibration (independent validation shown in parentheses)
R
2
and the root mean square error (RMSE) values, respectively, of 0.98 (0.97) and 0.10% (0.13%) for
N
mass
,
R
2
= 0.77 (0.73) and RMSE = 0.88% (0.95%) for
C
mass
,
R
2
= 0.89 (0.84) and RMSE = 2.8% (3.4%) for ADF,
R
2
= 0.77 (0.69) and RMSE = 2.4% (3.9%) for ADL,
R
2
= 0.77 (0.72) and RMSE = 1.4% (1.9%) for leaf cellulose,
R
2
= 0.62 (0.60) and RMSE = 0.91‰ (1.5‰) for δ
15
N, and
R
2
= 0.88 (0.87) with RMSE = 17.2 g/m
2
(22.8 g/m
2
) for
M
area
. This study demonstrates the potential for rapid and accurate estimation of key foliar traits of forest canopies that are important for ecological research and modeling activities, with a single calibration equation valid over a wide range of northern temperate and boreal species and leaf physiognomies. The results provide the basis to characterize important variability between and within species, and across ecological gradients using a rapid, cost-effective, easily replicated method.
Obesity is a risk factor for cardiovascular disease and death in people without chronic kidney disease (CKD), but the effect of obesity in people with CKD is uncertain.
Medline and Embase (from ...inception to January 2015) were searched for cohort studies measuring obesity by body mass index (BMI), waist:hip ratio (WHR) and/or waist circumference (WC) and all-cause and cardiovascular mortality or events in patients with any stage of CKD. Data were summarized using random effects models. Meta-regression was conducted to assess sources of heterogeneity.
Of 4065 potentially eligible citations, 165 studies ( n = 1 534 845 participants) were analyzed. In studies that found a nonlinear relationship, underweight people with CKD (3-5) on hemodialysis experienced an increased risk of death compared with those with normal weight. In transplant recipients, excess risk was observed at levels of morbid obesity (>35 kg/m 2 ). Of studies that found the relationship to be linear, a 1 kg/m 2 increase in BMI was associated with a 3 and 4% reduction in all-cause and cardiovascular mortality in patients on hemodialysis, respectively {adjusted hazard ratio HR 0.97 95% confidence interval (CI) 0.96-0.98 and adjusted HR 0.96 (95% CI 0.92-1.00)}. In CKD Stages 3-5, for every 1 kg/m 2 increase in BMI there was a 1% reduction in all-cause mortality HR 0.99 (95% CI 0.0.97-1.00). There was no apparent association between obesity and mortality in transplanted patients or those on peritoneal dialysis. Sparse data for WHR and WC did not allow further analyses.
Being obese may be protective for all-cause mortality in the predialysis and hemodialysis populations, while being underweight suggests increased risk, but not in transplant recipients.
Mortality risk after kidney transplantation can vary significantly during the post-transplant course. A contemporary assessment of trends in all-cause and cause-specific mortality at different ...periods post-transplant is required to better inform patients, clinicians, researchers, and policy makers.
We included all first kidney-only transplant recipients from 1980 through 2018 from the Australia and New Zealand Dialysis and Transplant Registry. We compared adjusted death rates per 5-year intervals, using a piecewise exponential survival model, stratified by time post-transplant or time post-graft failure.
Of 23,210 recipients, 4765 died with a functioning graft. Risk of death declined over successive eras, at all periods post-transplant. Reductions in early deaths were most marked; however, recipients ≥10 years post-transplant were 20% less likely to die in the current era compared with preceding eras (2015-2018 versus 2005-2009, adjusted hazard ratio, 0.80; 95% confidence interval, 0.69 to 0.90). In 2015-2018, cardiovascular disease was the most common cause of death, particularly in months 0-3 post-transplant (1.18 per 100 patient-years). Cancer deaths were rare early post-transplant, but frequent at later time points (0.93 per 100 patient-years ≥10 years post-transplant). Among 3657 patients with first graft loss, 2472 died and were not retransplanted. Death was common in the first year after graft failure, and the cause was most commonly cardiovascular (50%).
Reductions in death early and late post-transplant over the past 40 years represent a major achievement. Reductions in cause-specific mortality at all time points post-transplant are also apparent. However, relatively greater reductions in cardiovascular death have increased the prominence of late cancer deaths.
Recurrent glomerulonephritis after kidney transplantation is a feared complication because it is unpredictable and may have a negative impact on graft outcomes. To better understand this we collected ...data from the Australia and New Zealand Dialysis and Transplant (ANZDATA) Registry accumulated over 30 years. The incidence, risk factors, and outcomes of recurrent glomerulonephritis in transplant recipients were determined using adjusted Cox proportional hazard and competing risk modeling. A total of 6,597 recipients with biopsy-proven glomerulonephritis as the primary cause of end-stage kidney disease were followed for 51,871 person-years (median duration 7.7 years). The four most common types of glomerulonephritis were IgA nephropathy in 2501 patients, focal segmental glomerulosclerosis (FSGS) in 1403, membranous in 376, and membranoproliferative (MPGN) nephropathy in 357 patients. Among these four types, recurrence was reported in 479 of 4637 patients, and of these, 212 lost their allograft due to recurrence. Older age at transplantation (adjusted hazard ratio per year increase 0.96 95% confidence interval 0.95 – 0.97) was associated with a lower risk of recurrence. Significantly, the five-year graft survival was 30% for recipients with recurrent MPGN and 57-59% for recipients with FSGS, IgA, and membranous nephropathy. Transplant recipients with recurrent disease were twice as likely to lose their allografts compared to those without recurrence (adjusted hazard ratio 2.04 1.81-2.31). Thus, recurrent glomerulonephritis remains a significant cause of graft loss in transplant recipients.
Trials designed to assess the effect of interventions on death and graft failure in kidney transplant recipients are not feasible, because these are predominantly late events. Here, we examined the ...potential of percentage decline in eGFR as a surrogate for hard outcomes. We obtained deidentified data from the Australia and New Zealand Dialysis and Transplant Registry and studied 7949 transplants performed from 1995 to 2009, including 71,845 patient-years of follow-up, 1121 graft losses, and 1192 deaths. We used adjusted Cox proportional hazards models to determine risks of death or death-censored graft failure related to percentage change in eGFR between years 1 and 3 after transplant. Percentage change in eGFR was modeled as a restricted cubic spline. Rate of eGFR decline associated with exponentially increased risks of graft failure and death. Compared with stable eGFR, a ≥30% decline in eGFR, detected in 10% of patients, strongly associated with subsequent death (hazard ratio, 2.20; 95% confidence interval, 1.87 to 2.60) and death-censored graft failure (hazard ratio, 5.14; 95% confidence interval, 4.44 to 5.95). Decline in eGFR was superior to other surrogates, including acute rejection, doubling of serum creatinine level, and eGFR at year 1 or year 2. We conclude that 30% decline in eGFR between years 1 and 3 after kidney transplant is common and strongly associated with risks of subsequent death and death-censored graft failure, which mirrors findings in CKD. Percentage decline in eGFR should be considered for use as a surrogate outcome in kidney transplant trials.
Declining rates of acute rejection (AR) and the high rate of 1-year graft survival among patients with AR have prompted re-examination of AR as an outcome in the clinic and in trials. Yet AR and its ...treatment may directly or indirectly affect longer-term outcomes for kidney transplant recipients.
To understand the long-term effect of AR on outcomes, we analyzed data from the Australia and New Zealand Dialysis and Transplant Registry, including 13,614 recipients of a primary kidney-only transplant between 1997 and 2017 with at least 6 months of graft function. The associations between AR within 6 months post-transplant and subsequent cause-specific graft loss and death were determined using Cox models adjusted for baseline donor, recipient, and transplant characteristics.
AR occurred in 2906 recipients (21.4%) and was associated with graft loss attributed to chronic allograft nephropathy (hazard ratio HR, 1.39; 95% confidence interval 95% CI, 1.23 to 1.56) and recurrent AR beyond month 6 (HR, 1.85; 95% CI, 1.39 to 2.46). Early AR was also associated with death with a functioning graft (HR, 1.22; 95% CI, 1.08 to 1.36), and with death due to cardiovascular disease (HR, 1.30; 95% CI, 1.11 to 1.53) and cancer (HR, 1.35; 95% CI, 1.12 to 1.64). Sensitivity analyses restricted to subgroups with either biopsy-proven, antibody-mediated, or vascular rejection, or stratified by treatment response produced similar results.
AR is associated with increased risks of longer-term graft failure and death, particularly death from cardiovascular disease and cancer. The results suggest AR remains an important short-term outcome to monitor in kidney transplantation and clinical trials.
Serological surveys have been conducted to establish prevalence for COVID-19 antibodies in various cohorts and communities, reporting a wide range of outcomes. The prevalence of such antibodies among ...healthcare workers, presumed at higher risk for infection, has been increasingly investigated, more studies are needed to better understand the risks and infection transmission in different healthcare settings. The present study reports on initial sero-surveillance conducted on healthcare workers at a regional hospital system in Orange County, California, during May and June, 2020. Study subjects were recruited from the entire hospital employee workforce and the independent medical staff. Data were collected for job duties and locations, COVID-19 symptoms, a PCR test history, travel record since January 2020, and existence of household contacts with COVID-19. A blood sample was collected from each subject for serum analysis for IgG antibodies to SARS-CoV-2. Of 2,992 tested individuals, a total 2,924 with complete data were included in the analysis. Observed prevalence of 1.06% (31 antibody positive cases), adjusted prevalence of 1.13% for test sensitivity and specificity were identified. Significant group differences between positive vs. negative were observed for age (z = 2.65, p = .008), race (p = .037), presence of fever (p < .001), and loss of smell (p < .001), but not for occupations (p = .710). Possible explanation for this low prevalence includes a relatively low local geographic community prevalence (~4.4%) at the time of testing, the hospital's timely procurement of personal protective equipment, rigorous employee education, patient triage, and treatment protocol development and implementation. In addition, cross-reactive adaptive T cell mediated immunity, as recently described, may possibly play a greater role in healthcare workers than in the general population.
Celotno besedilo
Dostopno za:
DOBA, IZUM, KILJ, NUK, PILJ, PNG, SAZU, SIK, UILJ, UKNU, UL, UM, UPUK
To date, the utility of ecosystem and Earth system models (EESMs) has been limited by poor spatial and temporal representation of critical input parameters. For example, EESMs often rely on ...leaf-scale or literature-derived estimates for a key determinant of canopy photosynthesis, the maximum velocity of RuBP carboxylation (Vcmax, μmolm−2s−1). Our recent work (Ainsworth et al., 2014; Serbin et al., 2012) showed that reflectance spectroscopy could be used to estimate Vcmax at the leaf level. Here, we present evidence that imaging spectroscopy data can be used to simultaneously predict Vcmax and its sensitivity to temperature (EV) at the canopy scale. In 2013 and 2014, high-altitude Airborne Visible/Infrared Imaging Spectroscopy (AVIRIS) imagery and contemporaneous ground-based assessments of canopy structure and leaf photosynthesis were acquired across an array of monospecific agroecosystems in central and southern California, USA. A partial least-squares regression (PLSR) modeling approach was employed to characterize the pixel-level variation in canopy Vcmax (at a standardized canopy temperature of 30°C) and EV, based on visible and shortwave infrared AVIRIS spectra (414–2447nm). Our approach yielded parsimonious models with strong predictive capability for Vcmax (at 30°C) and EV (R2 of withheld data=0.94 and 0.92, respectively), both of which varied substantially in the field (≥1.7 fold) across the sampled crop types. The models were applied to additional AVIRIS imagery to generate maps of Vcmax and EV, as well as their uncertainties, for agricultural landscapes in California. The spatial patterns exhibited in the maps were consistent with our in-situ observations. These findings highlight the considerable promise of airborne and, by implication, space-borne imaging spectroscopy, such as the proposed HyspIRI mission, to map spatial and temporal variation in key drivers of photosynthetic metabolism in terrestrial vegetation.
•We measured photosynthetic capacity and its temperature response in California agroecosystems.•Photosynthetic traits were modeled from AVIRIS spectra using PLSR, with R2>0.92 and RMSE<10%.•Resulting maps of modeled photosynthetic traits matched the range of variation measured on the ground.
Objectives
To quantify the survival benefit of kidney transplantation for Aboriginal and Torres Strait Islander people waitlisted for deceased donor kidney transplantation in Australia.
Study design
...Retrospective cohort study; analysis of linked data from the Australia and New Zealand Dialysis and Transplant (ANZDATA) registry, the Australia and New Zealand Organ Donation (ANZOD) registry, and OrganMatch (Australian Red Cross).
Setting, participants
All adult Aboriginal and Torres Strait Islander people (18 years or older) who commenced dialysis in Australia during 1 July 2006 – 31 December 2020 and were included in the kidney‐only deceased donor transplant waiting list.
Main outcome measures
Survival benefit of deceased donor kidney transplantation relative to remaining on dialysis.
Results
Of the 4082 Aboriginal and Torres Strait Islander people who commenced dialysis, 450 were waitlisted for kidney transplants (11%), of whom 323 received deceased donor transplants. Transplantation was associated with a significant survival benefit compared with remaining on dialysis after the first 12 months (adjusted hazard ratio HR, 0.38; 95% confidence interval CI, 0.20–0.73). This benefit was similar to that for waitlisted non‐Indigenous people who received deceased donor kidney transplants (adjusted HR, 0.47; 95% CI, 0.40–0.57; Indigenous status interaction: P = 0.22).
Conclusions
From twelve months post‐transplantation, deceased donor transplantation provides a survival benefit for Aboriginal and Torres Strait Islander people. Our findings provide evidence that supports efforts to promote the waitlisting of Aboriginal and Torres Strait Islander people who are otherwise eligible for transplantation.
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