Milk metabolites for the detection of heat stress in dairy ruminants : Goats

Milk metabolites for the detection of heat stress in dairy ruminants: Goats The aim of this study was to analyze a group of milk metabolites used as heat stress (HS) biomarkers: i.e., alkaline phosphatase (ALP), β-hydroxybutyrate (BHB), creatinine (CRE) and insulin (INS), using reference methods and Near Infrared Reflectance Spectroscopy (NIRS) to calibrate and to predict the content of these HS biomarkers in the milk of ruminants. This study focuses on dairy goats. Citrate (CITR) and prolactin (PRL) were also analyzed but data was not available at the deadline of the Thesis. A total of 367 milk samples were obtained from 3 commercial farms (n = 311) and from the experimental group (n = 56) of the Universitat Autònoma of Barcelona (UAB). A subset of milk samples (n = 98) was used for analysis by standard laboratory methods and by NIRS (1,100 to 2,500 nm). Calibration and cross validation procedures were carried out for optimization with the UAB samples. Prediction accuracy for ALP and INS, according to their ratio of performance deviation (RPD) and range error ratio (RER) values, were acceptable (> 2 and >10, respectively). Additionally, values of the coefficient of determination for calibration (R2) were relatively good (0.97 and 0.96), indicating that they may be used for predicting ALP and INS in the milk of dairy goats. In conclusion, results from the biomarkers in milk demonstrated the reduction of ALP and INS in milk by effect of HS, thereby validating their use as HS indicators in the milk of dairy goats.Metabolitos en leche para la detección del estrés por calor en rumiantes lecheros: Cabras El objetivo de este estudio fue analizar un grupo de metabolitos de la leche utilizados como biomarcadores de estrés térmico (HS): es decir, fosfatasa alcalina (ALP), β- hidroxibutirato (BHB), creatinina (CRE) e insulina (INS), empleando métodos de referencia y Espectroscopia en el Infrarrojo Cercano (NIRS) para calibrar y para predecir el contenido de estos biomarcadores de HS en la leche de rumiantes. Este estudio se centra en cabras lecheras. También se analizaron citrato y prolactina, pero los datos no estaban disponibles en la fecha límite de la tesis. Se obtuvieron un total de 367 muestras de leche de 3 granjas comerciales (n= 311) y del grupo experimental (n= 56) de la Universitat Autònoma de Barcelona (UAB). Se utilizó un subconjunto de muestras de leche (n= 98) para el análisis por métodos de laboratorio estándar y por NIRS (1.100 a 2.500 nm). Se realizaron procedimientos de calibración y validación cruzada para la optimización con las muestras de la UAB. La precisión de predicción para ALP e INS, de acuerdo con su relación entre los valores de desviación de rendimiento (RPD) y relación de error de rango (RER), fueron aceptables (> 2 y >10, respectivamente). Además, los valores del coeficiente de determinación para la calibración (R2) eran relativamente buenos (0,97 y 0,96), indicando que se puede utilizar para predecir ALP e INS en la leche de cabras lecheras. En conclusión, los resultados de los biomarcadores en la leche demostraron la reducción de ALP e INS en la leche por efecto del HS, validando su uso como indicadores del HS en la leche de las cabras lecheras.Metabólitos lácteos para detecção de estresse térmico em ruminantes leiteiros: Cabras O objetivo deste estudo foi analisar um grupo de metabólitos lácteos utilizados como biomarcadores de (HS) estresse térmico: isto é, fosfatase alcalina (ALP), β- hidroxibutirato (BHB), creatinina (CRE) e insulina (INS), por métodos de referência e Espectroscopia no Infravermelho Próximo (NIRS) para calibrar e prever o conteúdo desses biomarcadores do HS no leite de ruminantes. Este estudo centra-se em cabras leiteiras. Citrato e prolactina também foram analisados, mas os dados não estavam disponíveis na data limite da tese. Um total de 367 mostras de leite foram obtidas de 3 fazendas comerciais (n= 311) e do grupo experimental (n= 56) da Universitat Autònoma de Barcelona (UAB). Um subconjunto de amostras de leite (n= 98) foi usado para análise por métodos laboratoriais e por NIRS (1.100 a 2.500 nm). Procedimentos de calibração e validação cruzada foram realizados para a otimização com as amostras da UAB. A precisão da previsão para ALP e INS, de acordo com os valores de relação de desempenho do desvio (RPD) e razão de intervalo de erro (RER), foram aceitáveis (> 2 y >10, respectivamente). Além disso, os valores do coeficiente de determinação da calibração (R2) foram relativamente bons (0,97 e 0,96) indicando que ele pode ser utilizado para predizer ALP e INS no leite de cabras leiteiras. Em conclusão, os resultados dos biomarcadores no leite demostraram a redução de ALP e INS sob efeito do HS, e validando seu uso como indicadores de HS em cabras leiteiras

Is there spin-charge separation in the 2D Hubbard and t-J models at low electronic densities?

The spin and density correlation functions of the two-dimensional Hubbard model at low electronic density $$ are calculated in the ground state by using the power method, and at finite temperatures by using the quantum Monte Carlo technique. Both approaches produce similar results, which are in close agreement with numerical and high temperature expansion results for the two-dimensional ${\rm t-J}$ model. Using perturbative approximations, we show that the examination of the density correlation function alone is not enough to support recent claims in the literature that suggested spin and charge separation in the low electronic density regime of the ${\rm t-J}$ model.Comment: 11 pages, tex, 3 figures upon request, NTHU - preprin

Crossover from two- to three-dimensional critical behavior for nearly antiferromagnetic itinerant electrons

The crossover from two- to three-dimensional critical behavior of nearly antiferromagnetic itinerant electrons is studied in a regime where the inter-plane single-particle motion of electrons is quantum-mechanically incoherent because of thermal fluctuations. This is a relevant regime for very anisotropic materials like the cuprates. The problem is studied within the Two-Particle Self-Consistent approach (TPSC), that has been previously shown to give a quantitative description of Monte Carlo data for the Hubbard model. It is shown that TPSC belongs to the $n\rightarrow \infty$ limit of the $O\left( n\right)$ universality class. However, contrary to the usual approaches, cutoffs appear naturally in the microscopic TPSC theory so that parameter-free calculations can be done for Hubbard models with arbitrary band structure. A general discussion of universality in the renormalized-classical crossover from $d=2$ to $d=3$ is also given.Comment: Revtex, 23 pages + 6 postcript figures (with epsfile

Symmetry breaking in the Hubbard model at weak coupling

The phase diagram of the Hubbard model is studied at weak coupling in two and three spatial dimensions. It is shown that the Neel temperature and the order parameter in d=3 are smaller than the Hartree-Fock predictions by a factor of q=0.2599. For d=2 we show that the self-consistent (sc) perturbation series bears no relevance to the behavior of the exact solution of the Hubbard model in the symmetry-broken phase. We also investigate an anisotropic model and show that the coupling between planes is essential for the validity of mean-field-type order parameters

Non-perturbative approach to the attractive Hubbard model

A non-perturbative approach to the single-band attractive Hubbard model is presented in the general context of functional derivative approaches to many-body theories. As in previous work on the repulsive model, the first step is based on a local-field type ansatz, on enforcement of the Pauli principle and a number of crucial sum-rules. The Mermin-Wagner theorem in two dimensions is automatically satisfied. At this level, two-particle self-consistency has been achieved. In the second step of the approximation, an improved expression for the self-energy is obtained by using the results of the first step in an exact expression for the self-energy where the high- and low-frequency behaviors appear separately. The result is a cooperon-like formula. The required vertex corrections are included in this self-energy expression, as required by the absence of a Migdal theorem for this problem. Other approaches to the attractive Hubbard model are critically compared. Physical consequences of the present approach and agreement with Monte Carlo simulations are demonstrated in the accompanying paper (following this one).Comment: Revtex, 19 page

Two-Particle-Self-Consistent Approach for the Hubbard Model

Even at weak to intermediate coupling, the Hubbard model poses a formidable challenge. In two dimensions in particular, standard methods such as the Random Phase Approximation are no longer valid since they predict a finite temperature antiferromagnetic phase transition prohibited by the Mermin-Wagner theorem. The Two-Particle-Self-Consistent (TPSC) approach satisfies that theorem as well as particle conservation, the Pauli principle, the local moment and local charge sum rules. The self-energy formula does not assume a Migdal theorem. There is consistency between one- and two-particle quantities. Internal accuracy checks allow one to test the limits of validity of TPSC. Here I present a pedagogical review of TPSC along with a short summary of existing results and two case studies: a) the opening of a pseudogap in two dimensions when the correlation length is larger than the thermal de Broglie wavelength, and b) the conditions for the appearance of d-wave superconductivity in the two-dimensional Hubbard model.Comment: Chapter in "Theoretical methods for Strongly Correlated Systems", Edited by A. Avella and F. Mancini, Springer Verlag, (2011) 55 pages. Misprint in Eq.(23) corrected (thanks D. Bergeron

Superconducting phase coherence in the presence of a pseudogap: Relation to specific heat, tunneling and vortex core spectroscopies

In this paper we demonstrate how, using a natural generalization of BCS theory, superconducting phase coherence manifests itself in phase insensitive measurements, when there is a smooth evolution of the excitation gap \Delta from above to below Tc. In this context, we address the underdoped cuprates. Our premise is that just as Fermi liquid theory is failing above Tc, BCS theory is failing below. The order parameter \Delta_{sc} is different from the excitation gap \Delta. Equivalently there is a (pseudo)gap in the excitation spectrum above Tc which is also present in the underlying normal state of the superconducting phase, and can be directly inferred from specific heat and vortex core experiments. At the same time many features of BCS theory, e.g., fermionic quasiparticles below Tc, are clearly present. These observations can be reconciled by a natural extension of BCS theory, which includes finite center-of-mass momentum pair excitations, in addition to the usual fermionic quasiparticles. Applying this theory we find that the Bose condensation of Cooper pairs, which is reflected in \Delta_{sc}, leads to sharp peaks in the spectral function once $T \le T_c$. These are manifested in ARPES spectra as well as in specific heat jumps, which become more like the behavior in a \lambda transition as the pseudogap develops. We end with a discussion of tunneling experiments and condensation energy issues. Comparison between theoretical and experimental plots of C_v, and of tunneling and vortex core spectroscopy measurements is good.Comment: 12 pages, 8 figures, ReVTeX 3.

Pairing fluctuations and pseudogaps in the attractive Hubbard model

The two-dimensional attractive Hubbard model is studied in the weak to intermediate coupling regime by employing a non-perturbative approach. It is first shown that this approach is in quantitative agreement with Monte Carlo calculations for both single-particle and two-particle quantities. Both the density of states and the single-particle spectral weight show a pseudogap at the Fermi energy below some characteristic temperature T*, also in good agreement with quantum Monte Carlo calculations. The pseudogap is caused by critical pairing fluctuations in the low-temperature renormalized classical regime $\omega < T$ of the two-dimensional system. With increasing temperature the spectral weight fills in the pseudogap instead of closing it and the pseudogap appears earlier in the density of states than in the spectral function. Small temperature changes around T* can modify the spectral weight over frequency scales much larger than temperature. Several qualitative results for the s-wave case should remain true for d-wave superconductors.Comment: 20 pages, 12 figure

‘Test Driving’ a Financing Instrument for Climate Adaptation: Analyzing Institutional Dilemmas using Simulation Gaming

Urban physical public infrastructure is a frontline defense mechanism to manage and mitigate climate-related impacts. Market instruments are often cited as possible means to spread risk and reduce financial burdens on the public sector. The authors argue that existing research tends to focus on the technical issues of instruments and neglects considering institutional dynamics that may enable or constrain local market-based financing mechanisms. In this article, three core dilemmas (values uncertainty, planning horizon, and indirect benefits) are used to analyze the responses of practitioners to a possible financing instrument. The findings indicate that the practitioner’s responses to tax increment financing were largely shaped by the adaptation dilemmas and not the characteristics of the instrument per se. By mapping the dilemmas onto whether they would recommend it, participants imposed a financial barrier on climate adaptation investments. The authors conclude that a key imperative in the design of policy instruments is to pay attention to the congruency of informal institutions at the ‘street level’ in order to be in-step with the current sociopolitical conditions. The findings also point to four key attributes that a local market-based instrument would need to be aligned and responsive to the Dutch planning and development context

Effects of different types of verbal encouragement on ankle force and muscle activity

The aim of this study is to investigate (i) the effect of live and recorded verbal encouragement on muscle activity and ankle force; (ii) the effect of communication/extroversion on the variables; (iii) the reliability intra and inter examiners of the variables. Twenty healthy-youngers were assessed by surface electromyography of tibialis anterior and ankle flexion force by an ergometer twice, with one week apart. No difference was found between ankle force (p = 0.373) and root mean square values (RMS) (p = 0.207) for any of the conditions assessed on day 1 nor between examiners 1 and 2 for both live and recorded conditions in RMS (p = 0.207) and force (p = 0.373). Between the 1st and 7th days, there were no differences for any of the conditions on RMS (main effect “Day” p = 0.261, “condition” p = 0.568, interaction p = 0.936) or force (main effect“Day” p = 0.889, “condition” p = 0.781, interaction p = 0.961). Intraclass correlation coefficients (ICCs) for the ankle force were, for without verbal encouragement (ICC2, k = 0.880), live verbal encouragement of examiner 1 (ICC2, k = 0.870), and recorded verbal encouragement of examiner 1 (ICC2, k = 0.920). RMS without verbal encouragement condition (ICC2, k = 0.860), live verbal encouragement of examiner 1 (ICC2, k = 0.930) and recorded verbal encouragement of examiner 1 (ICC2, k = 0.920). Reproducibility between the two examiner’s live encouragements for ankle force (ICC3, k = 0.981) and RMS (ICC3, k = 0.920). There was no effect of the presence or type of the augmented feedback in RMS and ankle force. We conclude that verbal encouragement does not influence ankle torque or muscle activity and there is good to excellent intra and inter rater reliability for subjects’ performance regardless of verbal encouragement modality. In addition, we observed that psychological traits Communication and Emotional stability does not affect the subjects’ strength performance at the ankle