Bootstrapping a powerful mixed portmanteau test for time series.

A new portmanteau test statistic is proposed for detecting nonlinearity in time series data. The new portmanteau statistic is calculated from the log of the determinant of a matrix comprised of the autocorrelations and cross-correlations of the residuals and squared residuals of a fitted time series. The asymptotic distribution of the proposed test statistic is derived as a linear combination of chi-square distributed random variables and can be approximated by a gamma distribution. A bootstrapping approach is shown to be robust when distributional assumptions are relaxed. The efficacy of the statistic is studied against linear and nonlinear dependency structures of some stationary time series models. It is shown that the new test can provide higher power than other tests in many situations. We demonstrate the advantages of the proposed test by investigating linear and nonlinear effects in an economic series and two environmental time series.

Routine postoperative noninvasive respiratory support and pneumonia after elective surgery: a systematic review and meta-analysis of randomised trials.

BACKGROUND: Postoperative pulmonary complications, including pneumonia, are a substantial cause of morbidity. We hypothesised that routine noninvasive respiratory support was associated with a lower incidence of pneumonia after surgery. METHODS: Systematic review and meta-analysis of RCTs comparing the routine use of continuous positive airway pressure (CPAP), noninvasive ventilation (NIV), or high-flow nasal oxygen (HFNO) against standard postoperative care in the adult population. We searched MEDLINE (PubMed), EMBASE, and CENTRAL from the start of indexing to July 27, 2021. Articles were reviewed and data extracted in duplicate, with discrepancies resolved by a senior investigator. The primary outcome was pneumonia, and the secondary outcome was postoperative pulmonary complications. We calculated risk difference (RD) with 95% confidence intervals using DerSimonian and Laird random effects models. We assessed risk of bias using the Cochrane risk of bias tool. RESULTS: From 18 513 records, we included 38 trials consisting of 9782 patients. Pneumonia occurred in 214/4403 (4.9%) patients receiving noninvasive respiratory support compared with 216/3937 (5.5%) receiving standard care (RD -0.01 [95% confidence interval: -0.02 to 0.00]; I2=8%; P=0.23). Postoperative pulmonary complications occurred in 393/1379 (28%) patients receiving noninvasive respiratory support compared with 280/902 (31%) receiving standard care (RD -0.11 [-0.23 to 0.01]; I2=79%; P=0.07). Subgroup analyses did not identify a benefit of CPAP, NIV, or HFNO in preventing pneumonia. Tests for publication bias suggest six unreported trials. CONCLUSION: The results of this evidence synthesis do not support the routine use of postoperative CPAP, NIV, or HFNO to prevent pneumonia after surgery in adults. CLINICAL TRIAL REGISTRATION: PROSPERO: CRD42019156741.

Testing for correlation between two time series using a parametric bootstrap.

We study the problem of determining if two time series are correlated in the mean and variance. Several test statistics, originally designed for determining the correlation between two mean processes or goodness-of-fit testing, are explored and formally introduced for determining cross-correlation in variance. Simulations demonstrate the theoretical asymptotic distribution can be ineffective in finite samples. Parametric bootstrapping is shown to be an effective tool in such an enterprise. A large simulation study is provided demonstrating the efficacy of the bootstrapping method. Lastly, an empirical example explores a correlation between the Standard & Poor's 500 index and the Euro/US dollar exchange rate while also demonstrating a level of robustness for the proposed method.

Correction: Dissolved organic matter protects mosquito larvae from damaging solar UV radiation.

[This corrects the article DOI: 10.1371/journal.pone.0240261.].

Dissolved organic matter protects mosquito larvae from damaging solar UV radiation.

Mosquitoes have increased in their abundance and geographic distribution in northeastern North America, coinciding with an increase in extreme precipitation events and up to a doubling of dissolved organic matter (DOM) concentrations in some inland waters. Increases in DOM can reduce exposure of mosquito larvae to solar ultraviolet (UV) radiation. Although mosquito larvae are most common in shaded habitats, almost nothing is known about their susceptibility to damage by solar UV radiation, or the ability of DOM to create a refuge from damaging UV in their shallow-water habitats. We hypothesize that 1) exposure to solar UV radiation is lethal to mosquito larvae, 2) larvae lack photo-enzymatic repair to fix UV-damaged DNA, and 3) DOM shades larvae from lethal solar UV radiation. We tested these hypotheses with experiments that manipulated UV radiation, the photo-repair radiation necessary for photo-enzymatic DNA repair, and DOM. Exposure to solar UV radiation significantly decreased larval survivorship, while DOM significantly increased it. There was no evidence of photo-enzymatic DNA repair. Our findings confirm that solar UV radiation decreases habitat suitability for mosquito larvae, but DOM provides a refuge from UV. This highlights the need for vector control managers to prioritize high DOM and shaded habitats in their efforts to reduce mosquito populations.

Changes in Internet Suicide Search Volumes Following Celebrity Suicides.

Celebrity suicides that are reported heavily in the media may increase risk for others' suicidal behavior. This study examined whether Internet search volumes for suicide-related terms changed after three celebrity suicide deaths (Robin Williams, Chester Bennington, and Alexander McQueen) and three celebrities who died by means other than suicide (David Bowie, Azzedine Alaia, and Paul Walker). Suicide search terms included suicide, how to suicide, commit suicide, depression, hanging, and suicide prevention. Observed suicide search volumes in the United States were collected from Google Trends for the 10 weeks before and the 2 weeks following each celebrity's death. Predicted search volumes for the 14 days postdeath were forecasted from the predeath search volumes and predicted search volumes were then compared to the true, observed search volumes. Search volumes for suicide terms significantly increased following Robin Williams' suicide death. Some of the terms increased in search volume following Chester Bennington's and Alexander McQueen's suicide deaths, but not significantly. Most search volumes for nonsuicide celebrity deaths did not change following their deaths. Celebrity suicide deaths can lead to significant, national increases in Internet search volumes for suicide-related terms for celebrities of high prominence. Results highlight the critical importance of reporting suicide deaths in the media responsibly.

Land cover impacts on storm flow suspended solid and nutrient concentrations in southwest Ohio streams.

Impacts between urban and agricultural land cover on storm flow water quality are poorly understood for the Eastern Corn Belt Ecoregion in SW Ohio. Storm flow water samples were collected from May 2017 to October 2017 across seven SW Ohio watersheds which ranged in urban land cover from 6% to 92% and in agricultural land cover from 4% to 70%. Two watersheds contained water resource recovery facilities (WRRFs). Percent agricultural land cover in a watershed and storm magnitude were primary explanatory variables for total suspended solid and total phosphorus concentrations. Total nitrogen, nitrate, and phosphate concentrations were primarily explained by the presence of WRRFs and percent agricultural land cover. Increased dissolved nutrient concentrations in watersheds with WRRFs indicate that WRRFs in the study area are ineffectively removing nitrate and phosphate from effluent. Results suggest that to improve water quality during storm flows, additional management efforts need to be focused on agricultural watersheds and WRRFs. PRACTITIONER POINTS: Storm flow water quality in the study area is significantly affected by land cover, WRRF Q, and storm Q. TSS and TP concentrations are best explained by percent of agricultural land cover in a watershed and magnitude of storms. TN, NO3 -N, and PO 4 3 -P concentrations are best explained by WRRF Q, followed by the percent agricultural land cover. This study shows that agricultural land cover and WRRFs play a significant role in water quality degradation in SW Ohio.

Stream Nitrogen, Phosphorus, and Sediment Concentrations Show Contrasting Long-term Trends Associated with Agricultural Change.

Stream water quality can be greatly influenced by changes in agricultural practices, but studies of long-term dynamics are scarce. Here we describe trends over 21 yr (1994-2014) in nutrients and suspended sediments in three streams in a Midwestern US agricultural watershed. During this time, the watershed experienced substantial changes in agricultural practices, most importantly a pronounced shift from conventional to conservation tillage. In the 1990s and early 2000s, NH, soluble reactive P, and suspended sediment concentrations (standardized for discharge and season) each declined significantly (>4-12% per year) in at least two of the three streams ( < 0.01), whereas NO changed relatively little. However, since the early 2000s, declines in NH and sediment concentrations have slowed, soluble reactive P concentrations have not declined and may actually have increased, and NO concentrations have declined sharply. The more recent lack of decline in soluble reactive P coincides with a plateau in the prevalence of conservation tillage and may be because of increased soil P stratification due to long-term reduced tillage. The more recent decline in NO may be due to improved efficiency of N fertilizer use, increased soil denitrification, and/or declines in atmospheric N deposition. Our study shows that stream concentrations of N, P, and sediment can respond in contrasting ways to changes in agriculture, and that temporal trends can moderate, accelerate, or reverse over decadal timescales. Management strategies must consider contrasting temporal responses of water quality indicators and may need to be adaptively adjusted at scales of years to decades.

Enantioselective Catalyst Systems from Copper(II) Triflate and BINOL-Silanediol.

Silanediol and copper catalysis are merged, for the first time, to create an enhanced Lewis acid catalyst system for enantioselective heterocycle functionalization. The promise of this silanediol and copper catalyst combination is demonstrated in the enantioselective addition of indoles to alkylidene malonates to give rise to the desirable adducts in excellent yield and high enantiomeric excess. From these studies, 1,1'-bi-2-naphthol (BINOL)-based silanediols emerge as one-of-a-kind cocatalysts. Their potential role in the reaction pathway is also discussed.

Do bacteria play an important role in the pathogenesis of low back pain?

Considerable interest has been generated recently regarding an alternative hypothesis for the pathogenesis of low back pain and radiculopathy in the presence of intervertebral disc prolapse. Traditionally, back pain and radicular (sciatic) symptoms have been attributed to mechanical compression of neural tissue by herniated disc material and to inflammation caused by exposure of the nerve roots to disc tissue. Recent research however has suggested that low-grade infection within the intervertebral disc by anaerobic bacteria may be responsible. The development of Modic changes in the corresponding adjacent vertebral endplates has also been suggested as an indicator of infection. This article is a thorough review of the current literature regarding the hypothesis that low-grade anaerobic bacterial infection may be the cause of disabling low back pain and radiculopathy.

Synthesis of α-peroxyesters via organocatalyzed O-H insertion of hydroperoxides and aryl diazoesters.

The synthesis of α-aryl peroxyesters, an unprecedented class of organic peroxide, via hydrogen-bond donor catalyzed O-H insertions of hydroperoxides and α-aryl diazoesters is reported. The method is applicable to a diverse set of substrates and the corresponding α-peroxyesters are typically isolated in high yield. Both thermogravimetric analysis and reactions with traditional peroxide reducing agents demonstrate the stability of α-peroxyesters.

Chiral silanediols in anion-binding catalysis.

A perfect pair: Silanediols are effective catalysts for the addition of silyl ketene acetals to N-acylisoquinolinium ions. Importantly, this is the first example of a silanediol plausibly participating in anion-binding catalysis, a relatively new direction in the field of hydrogen-bond-donor catalysis. The chiral, enantiopure C2 -symmetric silanediol 1 catalyzes enantioselective transformations.

Re2O7-catalyzed reaction of hemiacetals and aldehydes with O-, S-, and C-nucleophiles.

Re(VII) oxides catalyze the acetalization, monoperoxyacetalization, monothioacetalization and allylation of hemiacetals. The reactions, which take place under mild conditions and at low catalyst loadings, can be conducted using hemiacetals, the corresponding O-silyl ethers, and, in some cases, the acetal dimers. Aldehydes react under similar conditions to furnish good yields of dithioacetals. Reactions of hemiacetals with nitrogen nucleophiles are unsuccessful. 1,2-Dioxolan-3-ols (peroxyhemiacetals) undergo Re(VII)-promoted etherification but not allylation. Hydroperoxyacetals (1-alkoxyhydroperoxides) undergo selective exchange of the alkoxide group in the presence of either Re2O7 or a Brønsted acid.

Design and Synthesis of a New Class of Twin-Chain Amphiphiles for Self-Assembled Monolayer-based Electrochemical Biosensor Applications.

A new class of twin-chain hydroxyalkylthiols (mercaptoalkanols) featuring a nearly constant cross-section and the potential for modification of one or both termini are available with complete regioselectivity through Pd-mediated couplings of benzene diiododitriflate, including an example of a previously unreported coupling to generate an ortho-substituted arene bis acetic acid. Self-assembled monolayers (SAMs) prepared from the new amphiphiles demonstrate improved stability in an electrochemical sensor system compared with monolayers prepared from analogous single chain thiols.

Metachondromatosis: more than just multiple osteochondromas.

INTRODUCTION: Metachondromatosis is a rare genetic disease of osteochondroma and enchondroma formation, caused by loss of function of the PTPN11 gene. It is distinct from other similar conditions such as multiple osteochondromas and hereditary multiple exostoses by the distribution and orientation of lesions, and pattern of inheritance. Lesions typically occur in hands, feet, femora, tibiae and the pelvis. Lesions are typically reported to regress in adulthood. METHODS: We reviewed the current literature on metachondromatosis, and present four new cases in a family with metachondromatosis. RESULTS: Long-term follow up data reveal spontaneous regression of lesions by skeletal maturity. Complications may include nerve palsy due to the mass effect of lesions, avascular necrosis of the femoral head and angular deformity of long bones. Histopathological analysis has demonstrated that lesions in metachondromatosis are a mix of osteochondromas and enchondromas; however, one case of chondrosarcoma has been reported. CONCLUSION: Lesions associated with metachondromatosis may cause a variety of complications due to mass effects; however, they are often asymptomatic, cause cosmetic concerns and, importantly, most regress spontaneously. Regular clinical review with selective imaging to monitor for such complications is appropriate, but uncomplicated lesions are unlikely to require surgical intervention.

Pyridine is an organocatalyst for the reductive ozonolysis of alkenes.

Whereas the cleavage of alkenes by ozone typically generates peroxide intermediates that must be decomposed in an accompanying step, ozonolysis in the presence of pyridine directly generates ketones or aldehydes through a process that neither consumes pyridine nor generates any detectable peroxides. The reaction is hypothesized to involve nucleophile-promoted fragmentation of carbonyl oxides via formation of zwitterionic peroxyacetals.

GAL1-SceI directed site-specific genomic (gsSSG) mutagenesis: a method for precisely targeting point mutations in S. cerevisiae.

BACKGROUND: Precise targeted mutations are defined as targeted mutations that do not require the retention of other genetic changes, such as marker genes, near the mutation site. In the yeast, S. cerevisiae, there are several methods for introducing precise targeted mutations, all of which depend on inserting both a counter-selectable marker and DNA bearing the mutation. For example, the marker can first be inserted, and then replaced with either a long oligonucleotide carrying the mutation (delitto perfetto) or a PCR fragment synthesized with one primer containing the mutation (SSG mutagenesis). RESULTS: A hybrid method for targeting precise mutation into the genomes uses PCR fragments as in SSG mutagenesis together with a CORE cassette devised for delitto perfetto that contains the homing endonuclease SceI. This method, termed gsSSG mutagenesis, is much more efficient than standard SSG mutagenesis, allowing replacements to be identified without extensive screening of isolates. In gsSSG, recombination between the PCR fragment and the genome occurs equally efficiently regardless of the size of the fragment or the distance between the fragment end and the site of marker insertion. In contrast, the efficiency of incorporating targeted mutations by this method increases as the distance between the mutation and the marker insertion site decreases. CONCLUSION: gsSSG is an efficient way of introducing precise mutations into the genome of S. cerevisiae. The frequency of incorporating the targeted mutation remains efficient at least as far as 460 bp from the insertion site meaning that a single insertion can be used to create many different mutants. The overall efficiency of gsSSG can be estimated based on the distance between the mutation and the marker insertion, and this efficiency can be maximized by limiting the number of untargeted mutations. Thus, a single insertion of marker genes plus homing endonuclease cassette can be used to efficiently introduce precise point mutations through a region of > 900 bp.

Fragmentation of chloroperoxides: hypochlorite-mediated dehydration of hydroperoxyacetals to esters.

Hypochlorites efficently dehydrate hydroperoxyacetals to furnish the corresponding esters. The reaction, which can be accomplished with stoichometric Ca(OCl)(2) or with catalytic amounts of t-BuOCl, appears to involve formation and heterolytic fragmentation of secondary chloroperoxides, species not previously described in solution chemistry.