Proximate controls on semiarid soil greenhouse gas fluxes across 3 million years of soil development

Soils are important sources and sinks of three greenhouse gases (GHGs): carbon dioxide (CO2), methane (CH4), and nitrous oxide (N2O). However, it is unknown whether semiarid landscapes are important contributors to global fluxes of these gases, partly because our mechanistic understanding of soil GHG fluxes is largely derived from more humid ecosystems. We designed this study with the objective of identifying the important soil physical and biogeochemical controls on soil GHG fluxes in semiarid soils by observing seasonal changes in soil GHG fluxes across a three million year substrate age gradient in northern Arizona. We also manipulated soil nitrogen (N) and phosphorus availability with 7 years of fertilization and used regression tree analysis to identify drivers of unfertilized and fertilized soil GHG fluxes. Similar to humid ecosystems, soil N2O flux was correlated with changes in N and water availability and soil CO2 efflux was correlated with changes in water availability and temperature. Soil CH4 uptake was greatest in relatively colder and wetter soils. While fertilization had few direct effects on soil CH4 flux, soil nitrate was an important predictor of soil CH4 uptake in unfertilized soils and soil ammonium was an important predictor of soil CH4 uptake in fertilized soil. Like in humid ecosystems, N gas loss via nitrification or denitrification appears to increase with increases in N and water availability during ecosystem development. Our results suggest that, with some exceptions, the drivers of soil GHG fluxes in semiarid ecosystems are often similar to those observed in more humid ecosystems

Delayed Treatment and Missed Opportunities for Limb Salvage in Patients with Peripheral Arterial Embolism

BACKGROUND: The peripheral arterial embolism (PAE) is a sudden decrease in limb perfusion due to acute occlusion of peripheral artery which leads to ischemic tissue damage, that can threaten the limb of a patient and requires immediate revascularization. It is estimated that the incidence of acute limb emoblism in the general population is around 14/100,000 inhabitants per year. Accurate and timely diagnosis is crucial to salvage the patient’s limb and sometimes the patient’s life. In cases of complete arterial occlusion and absence of collateral perfusion, irreversible damage can occur within 4 to 6 hours. The fundamental definition for treatment of acute peripheral arterial embolism is revascularisation. Revascularisation is either performed endovascularly or by an open surgical approach. A suspicion of acute ischemia based on history and physical examination warrants heparin administration and vascular surgery consultation. Delays in the management of acute peripheral arterial ischemia due to an embolism are common and associated with poor limb - salvage outcomes. AIM: Our study aims to identify medical consultations and cardiovascular assessments undergone by patients in the period prior to being hospitalised, in order to evaluate for missed or delayed opportunities for diagnosis. METHODS: Retrospective cohort study, utilising the medical documentation and previous outpatiently or inhospital consultations. Adult patients undergone treatment due to peripheral arterial embolism were identified and analyzed. Patients were identified through the administrative hospital database using the International Classification of Diseases. Hospitalised patients with those medcodes between 1st January 2010 - 1st March 2020 were recorded. RESULTS: Following exclusion, 424 patients (mean age 68.5 ± 5.85 years) were included. 159 patients (66.8%) had visited their family doctors or other medical specialist before admission and in all of the cases was initiated therapeutic approach. The rest of the cohort 79 patients (33.2%) presented lately due to other social reasons. The group of 159 patients that admitted lately due to medical indications - diagnostic, healthcare - administrative or treatment related problems are subject of our study. The largest group including 113 (71%) patients were treated outpatientley by vascular surgeons with preventative medications.17 patients (10.6%) were directed outpatientley to orthopaedic surgeon due to suspicion of trauma.15 patients (9.4%) were treated by their family doctors with pain relief medications. The rest of the 14 patients (8.8%) were treated by neurosurgeons or neurologists due to a suspicion of cauda eniqua and other neuropathies. The majority of the patients 108 (67.9%) were free of complains at the discharge, 11.3% of the studied cohort were with minimal post-treatment complains (numbness, coldness, absent peripheral pulsations, insignificant claudicatio). Amputation rate was 14.4%, incidence of rethrombosis 8.8% and recurrent embolism frequency around 3.7%. Death was registered in 21 cases (13.2%). CONCLUSION: The consequences of acute limb embolism such as prolonged hospitalization, major limb amputation, and/or death have a profound socioeconomic impact. Unrecognition of this vascular pathology and differential diagnosis difficulties are possibly leading factors for delayed or missed treatment

Localized Structures in Indented Shells: A Numerical Investigation

We present results from a numerical investigation of the localization of deformation in thin elastomeric spherical shells loaded by differently shaped indenters. Beyond a critical indentation, the deformation of the shell ceases to be axisymmetric and sharp structures of localized curvature form, referred to as “s-cones,” for “shell-cones.” We perform a series of numerical experiments to systematically explore the parameter space. We find that the localization process is independent of the radius of the shell. The ratio of the radius of the shell to its thickness, however, is an important parameter in the localization process. Throughout, we find that the maximum principal strains remain below 6%, even at the s-cones. As a result, using either a linear elastic (LE) or hyperelastic constitutive description yields nearly indistinguishable results. Friction between the indenter and the shell is also shown to play an important role in localization. Tuning this frictional contact can suppress localization and increase the load-bearing capacity of the shell under indentation.National Science Foundation (U.S.) (1122374)National Science Foundation (U.S.) (CMMI-1351449

Neutrophil - Lymphocyte Ratio as a Reliable Predictor of Postoperative Outcome And Mortality In Delayed Cases Of Peripheral Arterial Embolism

Introduction: Peripheral arterial embolism (PAE) continues to pose a challenge to vascular surgeons and remains to be characterized by high morbidity, limb threat and mortality, often requiring urgent revascularization. Contemporary untreated arterial embolism is among the leading causes of morbidity and mortality within the vascular field. Detection of a fast and reliable biomarker for risk stratification and early post-treatment prognosis is important for those with PAE, so that individuals at high risk can be accurately treated and targeted for prevention. Complete blood count is inexpensive, comparatively routine, and is a practical laboratory test that gives important information about the patient’s formed blood contents. Routine peripheral blood counts may be useful in diagnosis and prognosis of many disorders, including peripheral vascular ischemic incidents. Neutrophil - lymphocyte ratio (NLR) has been shown to be an independent predictor of early and midterm amputation in patients with acute limb ischemia after revascularisation. Methods: Data was collected retrospectively from hospitalised patients, in the Vascular Surgery Clinic of University Hospital, Stara Zagora, Bulgaria, who had a diagnosis of PAE, from January 2010 to January 2019. Inclusion criteria were clinical data of an ischemic embolic incident of the limbs, untreated at least 12 hours from the onset of symptoms. Results: A single cutoff point was chosen to better inform clinical practice at a value of NLR 4.55, to maximize sensitivity and specificity. The majority of patients from the group Who had a NLR under 4.55 had mild symptoms. Older patients however, were significantly more likely to have an elevated NLR. The incidence of diabetes and hypertension were not significantly higher in any group. There was a higher incidence of primary major amputations in the elevated NLR group. Of the 25 deaths during the course of the study, which were specifically attributed to cardiac causes, twelve (13.8%) occurred within the elevated NLR group and thirteen (8.7%) in the low NLR group. Conclusion: NLR is an easily accessible biomarker that conveys important information about the patient’s inflammatory activity and can be easily calculated from the differential WBC count, which is routinely performed on admission and is universally available. An elevated NLR could potentially be included in addition to the most common risk factors for mortality and poor post-treatment outcome including cardiac causes, age >70 years, history of stroke or previous MI, renal failure, and smoking history (at any time)

Strain-stiffening in random packings of entangled granular chains

Random packings of granular chains are presented as a model polymer system to investigate the contribution of entanglements to strain-stiffening in the absence of Brownian motion. The chain packings are sheared in triaxial compression experiments. For short chain lengths, these packings yield when the shear stress exceeds a the scale of the confining pressure, similar to packings of spherical particles. In contrast, packings of chains which are long enough to form loops exhibit strain-stiffening, in which the effective stiffness of the material increases with strain, similar to many polymer materials. The latter packings can sustain stresses orders-of-magnitude greater than the confining pressure, and do not yield until the chain links break. X-ray tomography measurements reveal that the strain-stiffening packings contain system-spanning clusters of entangled chains.Comment: 4 pages, 4 figures. submitted to Physical Review Letter

A Systems Biology Approach to Identify Molecular Determinants of Resistance in Breast Cancer

De novo and acquired resistance to anti-estrogen therapy and aromatase inhibitors remains a challenge in the treatment of estrogen-receptor positive breast cancer. We employed a systems biology approach to identify survival determinants of estrogen independent breast cancer cells with varying sensitivities to hormonal therapeutics. An estrogen receptor-centered network was developed using bioinformatics databases to probe, with a network-targeted 631-element siRNA library, for essential genes involved in the proliferation and survival of estrogen independent breast cancer cells. We identified a unique subset of 25 genes that are essential for the proliferation of estrogen independent breast cancer cells, 15 of which also promote apoptosis.Ph.D., Biomedical Engineering -- Drexel University, 201

Cross Sections From Scalar Field Theory

A one pion exchange scalar model is used to calculate differential and total cross sections for pion production through nucleon- nucleon collisions. The collisions involve intermediate delta particle production and decay to nucleons and a pion. The model provides the basic theoretical framework for scalar field theory and can be applied to particle production processes where the effects of spin can be neglected

Localization of deformation in thin shells under indentation

Thesis: S.M., Massachusetts Institute of Technology, Department of Mechanical Engineering, 2013.Cataloged from PDF version of thesis.Includes bibliographical references (pages 72-77).We perform a hybrid experimental and numerical study of the localization of deformation in thin spherical elastic shells under indentation. Past a critical indentation, the deformation of the shell ceases to be axisymmetric and sharp points of localized curvature form. In plates, these sharp points are known as d-cones. By way of analogy, regions of localization in shells are referred to as s-cones, for 'shell-cones'. We quantify how the formation and evolution of s-cones is affected by the indenter's curvature. Juxtaposing results from precision model experiments and Finite Element simulations enables the exploration of the frictional nature of the shell-indenter contact. The numerics also allow for a characterization of the relative properties of strain energy focusing, at the different loci of localization. The predictive power of the numerics is taken advantage of to further explore parameter space and perform numerical experiments that are not easily conducted physically. This combined experimental and computational approach allows us to gain invaluable physical insight towards rationalizing this geometrically nonlinear process.by Alice M. Nasto.S.M

Benthic invertebrates associated with subfossil cold-water coral frames and hardgrounds in the Albanian deep waters (Adriatic sea)

The fauna collected associated with subfossil Lophelia pertusa and Dendrophyllia cornigera coral samples and hardgrounds from Albanian waters between 190–230 m is discussed. Eighty-three benthic species are recorded: 2 Foraminifera, 22 Porifera, 6 Cnidaria, 25 Mollusca, 14 Annelida, 1 Arthropoda, 12 Bryozoa, and 1 Echinodermata. Seventy-four species are new records for the poorly investigated Albanian deep waters