Probing the Role of the Barrier Layer in Magnetic Tunnel Junction Transport

Magnetic tunnel junctions with a ferrimagnetic barrier layer have been studied to understand the role of the barrier layer in the tunneling process - a factor that has been largely overlooked until recently. Epitaxial oxide junctions of highly spin polarized La0.7Sr0.3MnO3 and Fe3O4 electrodes with magnetic NiMn2O4 (NMO) insulating barrier layers provide a magnetic tunnel junction system in which we can probe the effect of the barrier by comparing junction behavior above and below the Curie temperature of the barrier layer. When the barrier is paramagnetic, the spin polarized transport is dominated by interface scattering and surface spin waves; however, when the barrier is ferrimagnetic, spin flip scattering due to spin waves within the NMO barrier dominates the transport.Comment: 10 pages, 3 figure

Stone-Wales Transformation Paths in Fullerene C60

The mechanisms of formation of a metastable defect isomer of fullerene C60 due to the Stone-Wales transformation are theoretically studied. It is demonstrated that the paths of the "dynamic" Stone-Wales transformation at a high sufficient for overcoming potential barriers) temperature can differ from the two "adiabatic" transformation paths discussed in the literature. This behavior is due to the presence of a great near-flat segment of the potential-energy surface in the neighborhood of metastable states. Besides, the sequence of rupture and formation of interatomic bonds is other than that in the case of the adiabatictransformation.Comment: 10 pages, 6 figure

Formation of Nitriles in the Interstellar Medium via Reactions of Cyano Radicals, CN(X 2Σ+), with Unsaturated Hydrocarbons

Crossed molecular beam experiments of cyano radicals, CN(X 2Σ+, ν = 0), in their electronic and vibrational ground state reacting with unsaturated hydrocarbons acetylene, C2H2(X 1Σ), ethylene, C2H4(X 1Ag), methylacetylene, CH3CCH(X 1A1), allene, H2CCCH2(X 1A1), dimethylacetylene, CH3CCCH3(X 1A1'), and benzene, C6H6 (X 1A1g), were performed at relative collision energies between 13.3 and 36.4 kJ mol-1 to unravel the formation of unsaturated nitriles in the outflows of late-type AGB carbon stars and molecular clouds. In all reactions, the CN radical was found to attack the π electron density of the hydrocarbon molecule with the radical center located at the carbon atom; the formation of an initial addition complex is a prevalent pathway on all the involved potential energy surfaces. A subsequent carbon-hydrogen bond rupture yields the nitriles cyanoacetylene, HCCCN (X 1Σ+), vinylcyanide, C2H3CN (X 1A'), 1-methylcyanoacetylene, CH3CCCN (X 1A1), cyanoallene, H2CCCH(CN) (X 1A'), 3-methylcyanoacetylene, HCCCH2CN(X 1A'), 1,1-cyanomethylallene, H2CCC(CN)(CH3) (X 1A'), and cyanobenzene, C6H5CN (X 1A1). In case of acetylene and ethylene, a second reaction channel involves a [1, 2]-H atom shift in the initial HCCHCN and H2CCH2CN collision complexes prior to a hydrogen atom release to form cyanoacetylene, HCCCN (X 1Σ+), and vinylcyanide, C2H3CN (X 1A'). Since all these radical-neutral reactions show no entrance barriers, have exit barriers well below the energy of the reactant molecules, and are exothermic, the explicit identification of this CN versus H atom exchange pathway under single collision conditions makes this reaction class a compelling candidate to synthesize unsaturated nitriles in interstellar environments holding temperatures as low as 10 K. This general concept makes it even feasible to predict the formation of nitriles once the corresponding unsaturated hydrocarbons are identified in the interstellar medium. Here HCCCN, C2H3CN, and CH3CCCN have been already observed; since CH3CCH is the common precursor to H2CCCH(CN)/CH3CCCN and the latter isomer has been assigned unambiguously toward TMC-1 and OMC-1, H2CCCH(CN) is strongly expected to be present in both clouds as well. The formation of isonitrile isomers was not observed in our experiments. Since all reactions to HCCNC, C2H3NC, CH3CCNC, H2CCCH(NC), H2CCC(NC)(CH3), and C6H5NC are either endothermic or the exit barrier is well above the energy of the reactants, neutral-neutral reactions of cyano radicals with closed shell unsaturated hydrocarbons cannot synthesize isonitriles in cold molecular clouds. However, in outflow of carbon stars, the enhanced translational energy of both reactants close to the photosphere of the central star can compensate this endothermicity, and isonitriles might be formed in these hotter environments as well

Human biogeography and faunal exploitation in Diamante River basin, central western Argentina

A biogeographic model used to describe human peopling of southern Mendoza, central western Argentina, proposed an intensification process activated by an increase in population growth rate during the Late Holocene. During this process, high-ranked resources at the surroundings of residential camps were depleted, and hunter–gatherers broadened their diet by incorporating a larger number of low-ranked prey and domesticated plant resources. In this paper, we evaluate an alternative hypothesis, focusing on zooarchaeological data from the Diamante River basin. The results show that faunal resource intensification does not appear to have occurred in the Diamante River basin during the Late Holocene. Faunal consumption in Diamante River basin mainly reflects the local fauna in each ecological zone. The data do not show a lack of higher ranked resources. We suggest it is more likely that the demographic increase was not significant enough to cause an impact on the faunal resources. The archaeological evidence should be improved and analysed in smaller scales to continue with the intensification debate.Fil: Otaola, Clara. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Provincia de Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Universidad Nacional de Cuyo. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; ArgentinaFil: Giardina, Miguel Angel. Consejo Nacional de Investigaciones Científicas y Técnicas. Centro Científico Tecnológico Conicet - Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Provincia de Mendoza. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales. Universidad Nacional de Cuyo. Instituto Argentino de Nivología, Glaciología y Ciencias Ambientales; ArgentinaFil: Franchetti, Fernando Ricardo. University of Pittsburgh at Johnstown; Estados Unidos. Consejo Nacional de Investigaciones Científicas y Técnicas; Argentin

GI Bleeding in the Elderly

Purpose: To determine the risk factors contributing to and etiologies of gastrointestinal bleeding in an elderly patient population seen by Southwest Gastroenterology (SWGA) providers. Methods: This study reviews charts of patients with GI bleeding from documented sources between 1/1999 and 3/2006. The cases are gathered retrospectively from the clinical records of SWGA, a 12-person private, single specialty gastroenterology group serving community hospitals. Etiology and risk factors for GI hemorrhages are recorded in an elderly population, defined as patients age 55 and older. Results: GI hemorrhages are identified in 105 patients. The majority (83, 79%) of hemorrhages are upper GI bleeds (UGIB) comparing to 22 (21%) lower GI bleeds (LGIB). In the UGIB group, the most common etiology of bleed is gastric ulcer (29%). We also found 72% of UGIB patients on prescribed anticoagulation medications, including anti-platelet agents or non-steroidal anti-inflammatory drugs (NSAIDs). 20% of these patients are also positive for H. Pylori. Thirty patients in the UGIB group smoke or consume alcohol heavily (consuming more than 3 drinks per day for men and two drinks per day for women) while 2 patients smoke or consume alcohol in the LGIB group. Previous bleeds are common in both groups with 39 (41%) in UGIB and 9 (47%) in LGIB. Co-morbidity is the most common risk factor with 20 (91%) in LGIB and 73 (88%) in UGIB. In the peptic ulcer disease (PUD) bleeds, the majority (77%) are taking NSAIDs, while in the non-PUD bleeds, only 38% are currently on NSAIDs. Overall, there are 2 mortalities resulting from cardiovascular complications of GI bleeding. Conclusion: The etiologies of GI bleeds in this population are comparable to other studies in the literature. The ratio of UGIB to LGIB in this elderly population is also similar to that reported in the literature. The risk factors shown to be most correlated to bleeding are co-morbidities, previous episodes of bleeding, anticoagulation, NSAID use, smoking and alcohol use. NSAID use is significant in PUD bleed patients. This study reinforces that increased knowledge of etiology, incidence and contributing factors of GI bleeding are necessary for physicians to efficiently treat GI bleeds in the elderly population

Impact of COVID-19 on 1-year survival outcomes in hepatocellular carcinoma: a multicenter cohort study

INTRODUCTION: The COVID-19 pandemic has caused severe disruption of healthcare services worldwide and interrupted patients' access to essential services. During the first lockdown, many healthcare services were shut to all but emergencies. In this study, we aimed to determine the immediate and long-term indirect impact of COVID-19 health services utilisation on hepatocellular cancer (HCC) outcomes. METHODS: A prospective cohort study was conducted from 1 March 2020 until 30 June 2020, correlating to the first wave of the COVID-19 pandemic. Patients were enrolled from tertiary hospitals in the UK and Germany with dedicated HCC management services. All patients with current or past HCC who were discussed at a multidisciplinary meeting (MDM) were identified. Any delay to treatment (DTT) and the effect on survival at one year were reported. RESULTS: The median time to receipt of therapy following MDM discussion was 49 days. Patients with Barcelona Clinic Liver Cancer (BCLC) stages-A/B disease were more likely to experience DTT. Significant delays across all treatments for HCC were observed, but delay was most marked for those undergoing curative therapies. Even though severe delays were observed in curative HCC treatments, this did not translate into reduced survival in patients. CONCLUSION: Interruption of routine healthcare services because of the COVID-19 pandemic caused severe delays in HCC treatment. However, DTT did not translate to reduced survival. Longer follow is important given the delay in therapy in those receiving curative therapy

Effect of logging wounds on diameter growth of beech (Fagus orientalis Lipsky) trees following selection cutting in Caspian forests of Iran

Background Logging damage to residual trees during selection cutting may lead to serious economic losses in terms of both timber quality and diameter growth reduction. In this study, we investigated the effect of logging operations on residual tree damage and the consequence of injuries on diameter growth in an uneven-aged mixed forest dominated by beech (Fagus orientalis Lipsky)

Structural characterization of cationic lipid–tRNA complexes

Despite considerable interest and investigations on cationic lipid–DNA complexes, reports on lipid–RNA interaction are very limited. In contrast to lipid–DNA complexes where lipid binding induces partial B to A and B to C conformational changes, lipid–tRNA complexation preserves tRNA folded state. This study is the first attempt to investigate the binding of cationic lipid with transfer RNA and the effect of lipid complexation on tRNA aggregation and condensation. We examine the interaction of tRNA with cholesterol (Chol), 1,2-dioleoyl-3-trimethylammonium-propane (DOTAP), dioctadecyldimethylammoniumbromide (DDAB) and dioleoylphosphatidylethanolamine (DOPE), at physiological condition, using constant tRNA concentration and various lipid contents. FTIR, UV-visible, CD spectroscopic methods and atomic force microscopy (AFM) were used to analyze lipid binding site, the binding constant and the effects of lipid interaction on tRNA stability, conformation and condensation. Structural analysis showed lipid–tRNA interactions with G–C and A–U base pairs as well as the backbone phosphate group with overall binding constants of KChol = 5.94 (± 0.8) × 104 M–1, KDDAB = 8.33 (± 0.90) × 105 M–1, KDOTAP = 1.05 (± 0.30) × 105 M–1 and KDOPE = 2.75 (± 0.50) × 104 M–1. The order of stability of lipid–tRNA complexation is DDAB > DOTAP > Chol > DOPE. Hydrophobic interactions between lipid aliphatic tails and tRNA were observed. RNA remains in A-family structure, while biopolymer aggregation and condensation occurred at high lipid concentrations