How Farm Families Make Decisions

A.E. Res. 79-

Permafrost, Lakes, and Climate-Warming Methane Feedback: What is the Worst We Can Expect?

http://globalchange.mit.edu/research/publications/2275Permafrost degradation is likely enhanced by climate warming. Subsequent landscape subsidence and hydrologic changes support expansion of lakes and wetlands. Their anaerobic environments can act as strong emission sources of methane and thus represent a positive feedback to climate warming. Using an integrated earth-system model framework, which considers the range of policy and uncertainty in climatechange projections, we examine the influence of near-surface permafrost thaw on the prevalence of lakes, its subsequent methane emission, and potential feedback under climate warming. We find that increases in atmospheric CH4 and radiative forcing from increased lake CH4 emissions are small, particularly when weighed against unconstrained human emissions. The additional warming from these methane sources, across the range of climate policy and response, is no greater than 0.1 C by 2100. Further, for this temperature feedback to be discernable by 2100 would require at least an order of magnitude larger methaneemission response. Overall, the biogeochemical climate-warming feedback from boreal and Arctic lake emissions is relatively small whether or not humans choose to constrain global emissions.This work was supported under the Department of Energy Climate Change Prediction Program Grant DE-PS02-08ER08-05. The authors gratefully acknowledge this as well as additional financial support provided by the MIT Joint Program on the Science and Policy of Global Change through a consortium of industrial sponsors and Federal grants. Development of the IGSM applied in this research is supported by the U.S. Department of Energy, Office of Science (DE-FG02-94ER61937); the U.S. Environmental Protection Agency, EPRI, and other U.S. government agencies and a consortium of 40 industrial and foundation sponsors

Model for Glass Transition in a Binary fluid from a Mode Coupling approach

We consider the Mode Coupling Theory (MCT) of Glass transition for a Binary fluid. The Equations of Nonlinear Fluctuating Hydrodynamics are obtained with a proper choice of the slow variables corresponding to the conservation laws. The resulting model equations are solved in the long time limit to locate the dynamic transition. The transition point from our model is considerably higher than predicted in existing MCT models for binary systems. This is in agreement with what is seen in Computer Simulation of binary fluids. fluids.Comment: 9 Pages, 3 Figure

Measuring proper motions of isolated neutron stars with Chandra

The excellent spatial resolution of the Chandra observatory offers the unprecedented possibility to measure proper motions at X-ray wavelength with relatively high accuracy using as reference the background of extragalactic or remote galactic X-ray sources. We took advantage of this capability to constrain the proper motion of RX J0806.4-4123 and RX J0420.0-5022, two X-ray bright and radio quiet isolated neutron stars (INSs) discovered by ROSAT and lacking an optical counterpart. In this paper, we present results from a preliminary analysis from which we derive 2 sigma upper limits of 76 mas/yr and 138 mas/yr on the proper motions of RX J0806.4-4123 and RX J0420.0-5022 respectively. We use these values together with those of other ROSAT discovered INSs to constrain the origin, distance and evolutionary status of this particular group of objects. We find that the tangential velocities of radio quiet ROSAT neutron stars are probably consistent with those of 'normal' pulsars. Their distribution on the sky and, for those having accurate proper motion vectors, their possible birth places, all point to a local population, probably created in the part of the Gould Belt nearest to the earth.Comment: 8 pages, 3 figures, to appear in Astrophysics and Space Science, in the proceedings of "Isolated Neutron Stars: from the Interior to the Surface", edited by D. Page, R. Turolla and S. Zan

Modelling of strain effects in manganite films

Thickness dependence and strain effects in films of $La_{1-x}A_xMnO_3$ perovskites are analyzed in the colossal magnetoresistance regime. The calculations are based on a generalization of a variational approach previously proposed for the study of manganite bulk. It is found that a reduction in the thickness of the film causes a decrease of critical temperature and magnetization, and an increase of resistivity at low temperatures. The strain is introduced through the modifications of in-plane and out-of-plane electron hopping amplitudes due to substrate-induced distortions of the film unit cell. The strain effects on the transition temperature and transport properties are in good agreement with experimental data only if the dependence of the hopping matrix elements on the $Mn-O-Mn$ bond angle is properly taken into account. Finally variations of the electron-phonon coupling linked to the presence of strain turn out important in influencing the balance of coexisting phases in the filmComment: 7 figures. To be published on Physical Review

Vascularização arterial e estrutura das tubas uterinas em caprinos sem raça definida

Thirty sets of genital organs from adult goats were collected in specialized slaughter houses. Two procedures were utilized in this experiment: 1) injection of red dyed neoprene latex 450 followed by fixation in a 10% formaldehyde water solution; 2) injection of cinabrium dyed gelatin followed by a diafanization process using the method of Spalteholz. It was observed that the vessels responsible for the blood irrigation of the womb tubes come from the ovarian arteries. The ovarian arteries in all samples had their origin in abdominal aortas varying only in their position, uterine, lateral or uterine lateral. Besides being responsible for the blood irrigation of the ovaries, the ovarian arteries also created branches to the womb. The womb tube divides into a mid tube artery, which irrigates the mid portions of the tubes and into a stream tube artery, which is responsible for the irrigation of the caudal portion of the womb tube and the extremity of the uterus. It also irrigates the skull tube artery, that originates from the womb tube artery and arterially supplies the skull portions of the womb tubes. Histologically, all the segments of the tubes (isthmus, phial and inphundibulum) showed a simple, cylindrical, ciliated epithelium and were also constituted by the mucous and the muscular layers by a serous membrane.Estudaram-se trinta conjuntos de órgãos genitais femininos de cabras sem raça definida, adultas, coletadas em abatedouros especializados. Foram usadas duas técnicas para este experimento: 1) injeção de látex Neoprene 450 corado em vermelho, seguida da fixação em solução aquosa de formol a 10%. 2) injeção de gelatina corada com cinábrio, seguida do processo de diafanização, pelo método de Spaltholz. Observou-se que os vasos destinados à irrigação sangüínea das tubas uterinas provêm das artérias ováricas. Em todos os espécimes (100%) as artérias ováricas tiveram sua origem na aorta abdominal ventralmente, lateralmente e ventrolateralmente ao vaso. As artérias ováricas, além de serem responsáveis pela irrigação sangüínea dos ovários, emitem ramos para as tubas uterinas. A artéria tubouterina subdivide-se em artérias tubárica média, a qual irriga as porções médias das tubas, e tubárica caudal, responsável pela irrigação das porções caudais das tubas uterinas e da extremidade cranial do corno uterino. A artéria tubárica cranial também originária da artéria tubouterina supre as porções craniais das tubas uterinas. Histologicamente, todos os segmentos tubáricos (istmo, ampola e infundíbulo) apresentaram epitélio simples, cilíndrico na mucosa, uma camada muscular e uma serosa

The predictive value of the modified early warning score for admission to the intensive care unit in patients with a hematologic malignancy – A multicenter observational study

Objectives: The modified early warning score (MEWS) is used to detect clinical deterioration of hospitalized patients. We aimed to investigate the predictive value of MEWS and derived quick Sequential Organ Failure Assessment (qSOFA) scores for intensive care unit admission in patients with a hematologic malignancy admitted to the ward. Design: Retrospective, observational study in two Dutch university hospitals. Setting: Data from adult patients with a hematologic malignancy, admitted to the ward over a 2-year period, were extracted from electronic patient files. Main outcome measures: Intensive care admission. Results: We included 395 patients with 736 hospital admissions; 2% (n = 15) of admissions resulted in admission to the intensive care unit. A higher MEWS (OR 1.5; 95 %CI 1.3–1.80) and qSOFA (OR 4.4; 95 %CI 2.1–9.3) were associated with admission. Using restricted cubic splines, a rise in the probability of admission for a MEWS ≥ 6 was observed. The AUC of MEWS for predicting admission was 0.830, the AUC of qSOFA was 0.752. MEWS was indicative for intensive care unit admission two days before admission. Conclusions: MEWS was a sensitive predictor of ICU admission in patients with a hematologic malignancy, superior to qSOFA. Future studies should confirm cut-off values and identify potential additional characteristics, to further enhance identification of critically ill hemato-oncology patients. Implications for Clinical Practice: The Modified Early Warning Score (MEWS) can be used as a tool for healthcare providers to monitor clinical deterioration and predict the need for intensive care unit admission in patients with a hematologic malignancy. Yet, consistent application and potential reevaluation of current thresholds is crucial. This will enable bedside nurses to more effectively identify patients needing adjunctive care, facilitating timely interventions and improved outcome.</p

Finite-Temperature Transport in Finite-Size Hubbard Rings in the Strong-Coupling Limit

We study the current, the curvature of levels, and the finite temperature charge stiffness, D(T,L), in the strongly correlated limit, U>>t, for Hubbard rings of L sites, with U the on-site Coulomb repulsion and t the hopping integral. Our study is done for finite-size systems and any band filling. Up to order t we derive our results following two independent approaches, namely, using the solution provided by the Bethe ansatz and the solution provided by an algebraic method, where the electronic operators are represented in a slave-fermion picture. We find that, in the U=\infty case, the finite-temperature charge stiffness is finite for electronic densities, n, smaller than one. These results are essencially those of spinless fermions in a lattice of size L, apart from small corrections coming from a statistical flux, due to the spin degrees of freedom. Up to order t, the Mott-Hubbard gap is \Delta_{MH}=U-4t, and we find that D(T) is finite for n<1, but is zero at half-filling. This result comes from the effective flux felt by the holon excitations, which, due to the presence of doubly occupied sites, is renormalized to \Phi^{eff}=\phi(N_h-N_d)/(N_d+N_h), and which is zero at half-filling, with N_d and N_h being the number of doubly occupied and empty lattice sites, respectively. Further, for half-filling, the current transported by any eigenstate of the system is zero and, therefore, D(T) is also zero.Comment: 15 pages and 6 figures; accepted for PR

Protein biomarkers in blood reflect the interrelationships between stroke outcome, inflammation, coagulation, adhesion, senescence and cancer

The most important predictors for outcomes after ischemic stroke, that is, for health deterioration and death, are chronological age and stroke severity; gender, genetics and lifestyle/environmental factors also play a role. Of all these, only the latter can be influenced after the event. Recurrent stroke may be prevented by antiaggregant/anticoagulant therapy, angioplasty of high-grade stenoses, and treatment of cardiovascular risk factors. Blood cell composition and protein biomarkers such as C-reactive protein or interleukins in serum are frequently considered as biomarkers of outcome. Here we aim to provide an up-to-date protein biomarker signature that allows a maximum of mechanistic understanding, to predict health deterioration following stroke. We thus surveyed protein biomarkers that were reported to be predictive for outcome after ischemic stroke, specifically considering biomarkers that predict long-term outcome (≥ 3 months) and that are measured over the first days following the event. We classified the protein biomarkers as immune‑inflammatory, coagulation-related, and adhesion-related biomarkers. Some of these biomarkers are closely related to cellular senescence and, in particular, to the inflammatory processes that can be triggered by senescent cells. Moreover, the processes that underlie inflammation, hypercoagulation and cellular senescence connect stroke to cancer, and biomarkers of cancer-associated thromboembolism, as well as of sarcopenia, overlap strongly with the biomarkers discussed here. Finally, we demonstrate that most of the outcome-predicting protein biomarkers form a close-meshed functional interaction network, suggesting that the outcome after stroke is partially determined by an interplay of molecular processes relating to inflammation, coagulation, cell adhesion and cellular senescence

Branch-and-lift algorithm for deterministic global optimization in nonlinear optimal control

This paper presents a branch-and-lift algorithm for solving optimal control problems with smooth nonlinear dynamics and potentially nonconvex objective and constraint functionals to guaranteed global optimality. This algorithm features a direct sequential method and builds upon a generic, spatial branch-and-bound algorithm. A new operation, called lifting, is introduced, which refines the control parameterization via a Gram-Schmidt orthogonalization process, while simultaneously eliminating control subregions that are either infeasible or that provably cannot contain any global optima. Conditions are given under which the image of the control parameterization error in the state space contracts exponentially as the parameterization order is increased, thereby making the lifting operation efficient. A computational technique based on ellipsoidal calculus is also developed that satisfies these conditions. The practical applicability of branch-and-lift is illustrated in a numerical example. © 2013 Springer Science+Business Media New York