25 research outputs found
Nest-defense Behavior of Mississippi Kites in Urban and Exurban Areas
Mississippi kites (Ictinia mississippiensis) have become an abundant raptor in many urban and exurban areas throughout the Southern Great Plains of the United States. Unfortunately, human–wildlife conflicts have resulted from this juxtaposition of suitable breeding areas for kites and areas that humans frequent, with some kites responding aggressively to humans near nests. To date, there are no data describing the prevalence of aggressive nest defense in the species, making informed management of human and kite conflicts difficult. We assessed and compared the prevalence of aggressive nest-defense by Mississippi kites in an urban area and an exurban area by simulating nest disturbance with a trial pedestrian. Additionally, we examine the relationships between physical features of the nest tree where aggressive behaviors were and were not recorded. Individual kites breeding in the exurban area responded to the trial pedestrian by taking flight from the nesting area, circling overhead, swooping at the pedestrian, or remaining on the nest. In the urban area, kites displayed a more limited suit of responses and either remained on the nest or swooped at the pedestrian. Additionally, kites breeding in the exurban area appeared to respond to experimental disturbance at a greater distance than did urban breeding kites, but not with more attacks on pedestrians. Physical characteristics of the nest tree did not explain aggressive behaviors, thereby suggesting that aggression in Mississippi kites is caused by factors other than nesting location features
Triptycene Structure-Directing Agents in Aluminophosphate Synthesis
The synthesis of aluminophosphates is investigated using a number of triptycene-based organic structure-directing agents (OSDA). These OSDAs are designed to synthesize extra-large pore and/or large cavity-containing molecular sieves. Starting from the hydrophobic triptycene molecule, OSDAs are prepared by introducing three amine-based centers that can be charged either by protonation in the acidic aluminophosphate reaction media or through quaternization. VPI-5 is synthesized using these tripytycene OSDAs, and the OSDAs are occluded inside the pores. This synthesis marks the first time VPI-5 has been made as a single phase with an OSDA occluded inside the framework of the as-made material that is not removed by simple washing with water or other solvents. Additionally, several other aluminophosphates with unknown structures are synthesized using these new OSDAs
Facile Synthesis and Catalysis of Pure-Silica and Heteroatom LTA
Zeolite A (LTA) has many large-scale uses in separations and ion exchange applications. Because of the high aluminum content and lack of high-temperature stability, applications in catalysis, while highly desired, have been extremely limited. Herein, we report a robust method to prepare pure-silica, aluminosilicate (product Si/Al = 12–42), and titanosilicate LTA in fluoride media using a simple, imidazolium-based organic structure-directing agent. The aluminosilicate material is an active catalyst for the methanol-to-olefins reaction with higher product selectivities to butenes as well as C_5 and C_6 products than the commercialized silicoalumniophosphate or zeolite analogue that both have the chabazite framework (SAPO-34 and SSZ-13, respectively). The crystal structures of the as-made and calcined pure-silica materials were solved using single-crystal X-ray diffraction, providing information about the occluded organics and fluoride as well as structural information
Mortality and pulmonary complications in patients undergoing surgery with perioperative SARS-CoV-2 infection: an international cohort study
Background: The impact of severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) on postoperative recovery needs to be understood to inform clinical decision making during and after the COVID-19 pandemic. This study reports 30-day mortality and pulmonary complication rates in patients with perioperative SARS-CoV-2 infection. Methods: This international, multicentre, cohort study at 235 hospitals in 24 countries included all patients undergoing surgery who had SARS-CoV-2 infection confirmed within 7 days before or 30 days after surgery. The primary outcome measure was 30-day postoperative mortality and was assessed in all enrolled patients. The main secondary outcome measure was pulmonary complications, defined as pneumonia, acute respiratory distress syndrome, or unexpected postoperative ventilation. Findings: This analysis includes 1128 patients who had surgery between Jan 1 and March 31, 2020, of whom 835 (74·0%) had emergency surgery and 280 (24·8%) had elective surgery. SARS-CoV-2 infection was confirmed preoperatively in 294 (26·1%) patients. 30-day mortality was 23·8% (268 of 1128). Pulmonary complications occurred in 577 (51·2%) of 1128 patients; 30-day mortality in these patients was 38·0% (219 of 577), accounting for 81·7% (219 of 268) of all deaths. In adjusted analyses, 30-day mortality was associated with male sex (odds ratio 1·75 [95% CI 1·28–2·40], p\textless0·0001), age 70 years or older versus younger than 70 years (2·30 [1·65–3·22], p\textless0·0001), American Society of Anesthesiologists grades 3–5 versus grades 1–2 (2·35 [1·57–3·53], p\textless0·0001), malignant versus benign or obstetric diagnosis (1·55 [1·01–2·39], p=0·046), emergency versus elective surgery (1·67 [1·06–2·63], p=0·026), and major versus minor surgery (1·52 [1·01–2·31], p=0·047). Interpretation: Postoperative pulmonary complications occur in half of patients with perioperative SARS-CoV-2 infection and are associated with high mortality. Thresholds for surgery during the COVID-19 pandemic should be higher than during normal practice, particularly in men aged 70 years and older. Consideration should be given for postponing non-urgent procedures and promoting non-operative treatment to delay or avoid the need for surgery. Funding: National Institute for Health Research (NIHR), Association of Coloproctology of Great Britain and Ireland, Bowel and Cancer Research, Bowel Disease Research Foundation, Association of Upper Gastrointestinal Surgeons, British Association of Surgical Oncology, British Gynaecological Cancer Society, European Society of Coloproctology, NIHR Academy, Sarcoma UK, Vascular Society for Great Britain and Ireland, and Yorkshire Cancer Research
Assessment of Frequency and Duration of Point Counts When Surveying for Golden Eagle Presence
We assessed the utility of the recommended golden eagle (Aquila chrysaetos) surveymethodology in the U.S. Fish and Wildlife Service 2013 Eagle Conservation Plan Guidance. We conducted800-m radius, 1-hr point-count surveys broken into 20-min segments, during 2 sampling periods in 3 areaswithin the Intermountain West of the United States over 2 consecutive breeding seasons during 2012 and2013. Our goal was to measure the influence of different survey time intervals and sampling periods ondetectability and use estimates of golden eagles among different locations. Our results suggest that a lessintensive effort (i.e., survey duration shorter than 1 hr and point-count survey radii smaller than 800 m)would likely be inadequate for rigorous documentation of golden eagle occurrence pre- or postconstruction ofwind energy facilities. Results from a simulation analysis of detection probabilities and survey effort suggestthat greater temporal and spatial effort could make point-count surveys more applicable for evaluating goldeneagle occurrence in survey areas; however, increased effort would increase financial costs associated withadditional person-hours and logistics (e.g., fuel, lodging). Future surveys can benefit from a pilot study andcareful consideration of prior information about counts or densities of golden eagles in the survey area beforedeveloping a survey design. If information is lacking, survey planning may be best served by assuming lowdetection rates and increasing the temporal and spatial effort. Published 2017. This article is a U.S.Government work and is in the public domain in the USA
Synthesis of Germanosilicate Molecular Sieves from Mono- and Di-Quaternary Ammonium OSDAs Constructed from Benzyl Imidazolium Derivatives: Stabilization of Large Micropore Volumes Including New Molecular Sieve CIT-13
A series of monoquaternary and diquarternary benzyl-imidazolium derivatives are prepared and used as organic structure direction agents (OSDAs) in germanosilicate syntheses. The goal of this work is to create new multidimensional large pore zeolites. For the OSDA made and tested, we looked for relationships based upon stereochemistry from the benzyl ring as part of each structure. Several known molecular sieves with the *BEA, BEC, IWS, or LTA topologies are obtained. Molecular modeling is carried out with the goal of understanding: (a) the product selectivity correlation with the OSDA and the zeolite obtained, and (b) why differential rates of crystallization are observed for isomers that lead to different zeolite products. Additionally, a new molecular sieve denoted CIT-13 is prepared and shown to possess intersecting 14- and 10-membered ring pores, which gives confidence to the soundness of this approach for OSDA construction to yield new multidimensional large pore zeolites. CIT-13 is the first molecular sieve to have this combination of pore sizes
Total Synthesis of the Akuammiline Alkaloid Picrinine
We report the first total synthesis
of the complex akuammiline
alkaloid picrinine, which was first isolated nearly five decades ago.
Our synthetic approach features a concise assembly of the [3.3.1]-azabicyclic
core, a key Fischer indolization reaction to forge the natural product’s
carbon framework, and a series of delicate late-stage transformations
to complete the synthesis. Our synthesis of picrinine also constitutes
a formal synthesis of the related polycyclic alkaloid strictamine
Fischer Indolizations as a Strategic Platform for the Total Synthesis of Picrinine
Picrinine,
which is a member of the akuammiline family of alkaloids,
was first isolated in 1965 from the leaves of <i>Alstonia scholaris</i>. The natural product possesses a daunting polycyclic skeleton that
contains a furanoindoline, a bridged [3.3.1]Âazabicycle, two <i>N</i>,<i>O</i>-acetal linkages, and six stereogenic
centers. These structural features render picrinine a challenging
and attractive target for total synthesis. This paper provides a full
account of our synthetic forays toward picrinine, which culminates
in the first total synthesis of this long-standing target. Central
to the success of our approach is the use of the Fischer indolization
reaction to introduce the C7 quaternary stereocenter and the indoline
nucleus of the natural product’s scaffold. We probe some of
the subtleties of this classic transformation by examining some of
the most complex Fischer indolization substrates to date. Additionally,
we describe various roadblocks encountered in our experimental efforts,
which were successfully overcome to complete the total synthesis of
picrinine