Effect of High Pressure Homogenization Process on Bacillus Stearothermophilus and Clostridium Sporogenes Spores in Skim Milk

AbstractHigh pressure homogenization (HPH) is an alternative food processing technique. As product heating is minimum, its characteristics are not affected in a large extend. This characteristic makes the HPH an interesting process to guarantee the safety of thermo-labile food. Inactivation of Bacillus stearothermophilus ATCC 7953 and Clostridium sporogenes PA 3679 spores in skim milk by HPH was studied. Results showed that pressures up to 300 MPa were not able to cause any reduction on spore counts or promote changes on its thermal resistance. The application of heat shock (100°C/15 min) before HPH treatment and the homogenization process realized at mild inlet temperature (45°C) – which results in homogenization temperature of around 84°C at 300 MPa - also did not cause reduction on viable spores counts. A few spores reduction (0.67 logarithmic cycles) were only observed when the milk samples were subjected to homogenization treatment 16 times (multiple passes) at 300 MPa. Therefore, although HPH be recognized as an effective method for milk pasteurization, it was conclude that the HPH process is not able to guarantee the commercial sterility of milk, being necessary the association of the homogenization with another preservative method, as refrigeration

Increasing the detectability of external influence on precipitation by correcting feature location in GCMs

Understanding how precipitation varies as the climate changes is essential to determining the true impact of global warming. This is a difficult task not only due to the large internal variability observed in precipitation but also because of a limited historical record and large biases in simulations of precipitation by general circulation models (GCMs). Here we make use of a technique that spatially and seasonally transforms GCM fields to reduce location biases and investigate the potential of this bias correction to study historical changes. We use two versions of this bias correction—one that conserves intensities and another that conserves integrated precipitation over transformed areas. Focussing on multimodel ensemble means, we find that both versions reduce RMS error in the historical trend by approximately 11% relative to the Global Precipitation Climatology Project (GPCP) data set. By regressing GCMs' historical simulations of precipitation onto radiative forcings, we decompose these simulations into anthropogenic and natural time series. We then perform a simple detection and attribution study to investigate the impact of reducing location biases on detectability. A multiple ordinary least squares regression of GPCP onto the anthropogenic and natural time series, with the assumptions made, finds anthropogenic detectability only when spatial corrections are applied. The result is the same regardless of which form of conservation is used and without reducing the dimensionality of the fields beyond taking zonal means. While “detectability” is dependent both on the exact methodology and the confidence required, this nevertheless demonstrates the potential benefits of correcting location biases in GCMs when studying historical precipitation, especially in cases where a signal was previously undetectable

Magnetic ordering, electronic structure and magnetic anisotropy energy in the high-spin Mn10_{10} single molecule magnet

We report the electronic structure and magnetic ordering of the single molecule magnet [Mn$_{10}$O$_{4}$(2,2'-biphenoxide)$_{4}$Br$_{12}$]$^{4-}$ based on first-principles all-electron density-functional calculations. We find that two of the ten core Mn atoms are coupled antiferromagnetically to the remaining eight, resulting in a ferrimagnetic ground state with total spin S=13. The calculated magnetic anisotropy barrier is found to be 9 K in good agreement with experiment. The presence of the Br anions impact the electronic structure and therefore the magnetic properties of the 10 Mn atoms. However, the electric field due to the negative charges has no significant effect on the magnetic anisotropy.Comment: 4 pages, submitted to PR

Nanoelectromechanics of Piezoresponse Force Microscopy

To achieve quantitative interpretation of Piezoresponse Force Microscopy (PFM), including resolution limits, tip bias- and strain-induced phenomena and spectroscopy, analytical representations for tip-induced electroelastic fields inside the material are derived for the cases of weak and strong indentation. In the weak indentation case, electrostatic field distribution is calculated using image charge model. In the strong indentation case, the solution of the coupled electroelastic problem for piezoelectric indentation is used to obtain the electric field and strain distribution in the ferroelectric material. This establishes a complete continuum mechanics description of the PFM contact mechanics and imaging mechanism. The electroelastic field distribution allows signal generation volume in PFM to be determined. These rigorous solutions are compared with the electrostatic point charge and sphere-plane models, and the applicability limits for asymptotic point charge and point force models are established. The implications of these results for ferroelectric polarization switching processes are analyzed.Comment: 81 pages, 19 figures, to be published in Phys. Rev.

Traditional and Health-Related Philanthropy: The Role of Resources and Personality

I study the relationships of resources and personality characteristics to charitable giving, postmortem organ donation, and blood donation in a nationwide sample of persons in households in the Netherlands. I find that specific personality characteristics are related to specific types of giving: agreeableness to blood donation, empathic concern to charitable giving, and prosocial value orientation to postmortem organ donation. I find that giving has a consistently stronger relation to human and social capital than to personality. Human capital increases giving; social capital increases giving only when it is approved by others. Effects of prosocial personality characteristics decline at higher levels of these characteristics. Effects of empathic concern, helpfulness, and social value orientations on generosity are mediated by verbal proficiency and church attendance.

A particle-number-conserving Bogoliubov method which demonstrates the validity of the time-dependent Gross-Pitaevskii equation for a highly condensed Bose gas

The Bogoliubov method for the excitation spectrum of a Bose-condensed gas is generalized to apply to a gas with an exact large number $N$ of particles. This generalization yields a description of the Schr\"odinger picture field operators as the product of an annihilation operator $A$ for the total number of particles and the sum of a ``condensate wavefunction'' $\xi(x)$ and a phonon field operator $\chi(x)$ in the form $\psi(x) \approx A\{\xi(x) + \chi(x)/\sqrt{N}\}$ when the field operator acts on the N particle subspace. It is then possible to expand the Hamiltonian in decreasing powers of $\sqrt{N}$, an thus obtain solutions for eigenvalues and eigenstates as an asymptotic expansion of the same kind. It is also possible to compute all matrix elements of field operators between states of different N.Comment: RevTeX, 11 page

Natural variation in Arabidopsis thaliana reveals shoot ionome, biomass, and gene expression changes as biomarkers for zinc deficiency tolerance

Zinc (Zn) is an essential nutrient for plants, with a crucial role as a cofactor for many enzymes. Approximately one-third of the global arable land area is Zn deficient, leading to reduced crop yield and quality. To improve crop tolerance to Zn deficiency, it is important to understand the mechanisms plants have adopted to tolerate suboptimal Zn supply. In this study, physiological and molecular aspects of traits related to Zn deficiency tolerance were examined in a panel of 19 Arabidopsis thaliana accessions. Accessions showed a larger variation for shoot biomass than for Zn concentration, indicating that they have different requirements for their minimal Zn concentration required for growth. Accessions with a higher tolerance to Zn deficiency showed an increased expression of the Zn deficiency-responsive genes ZIP4 and IRT3 in comparison with Zn deficiency-sensitive accessions. Changes in the shoot ionome, as a result of the Zn treatment of the plants, were used to build a multinomial logistic regression model able to distinguish plants regarding their Zn nutritional status. This set of biomarkers, reflecting the A. thaliana response to Zn deficiency and Zn deficiency tolerance, can be useful for future studies aiming to improve the performance and Zn status of crop plants grown under suboptimal Zn concentrations

Amyloid-β oligomerization monitored by single-molecule stepwise photobleaching

A major hallmark of Alzheimer’s disease is the misfolding and aggregation of the amyloid- β peptide (Aβ). While early research pointed towards large fibrillar- and plaque-like aggregates as being the most toxic species, recent evidence now implicates small soluble Aβ oligomers as being orders of magnitude more harmful. Techniques capable of characterizing oligomer stoichiometry and assembly are thus critical for a deeper understanding of the earliest stages of neurodegeneration and for rationally testing next-generation oligomer inhibitors. While the fluorescence response of extrinsic fluorescent probes such as Thioflavin-T have become workhorse tools for characterizing large Aβ aggregates in solution, it is widely accepted that these methods suffer from many important drawbacks, including an insensitivity to oligomeric species. Here, we integrate several biophysics techniques to gain new insight into oligomer formation at the single-molecule level. We showcase single-molecule stepwise photobleaching of fluorescent dye molecules as a powerful method to bypass many of the traditional limitations, and provide a step-by-step guide to implementing the technique in vitro. By collecting fluorescence emission from single Aβ(1–42) peptides labelled at the N-terminal position with HiLyte Fluor 555 via wide-field total internal reflection fluorescence (TIRF) imaging, we demonstrate how to characterize the number of peptides per single immobile oligomer and reveal heterogeneity within sample populations. Importantly, fluorescence emerging from Aβ oligomers cannot be easily investigated using diffraction-limited optical microscopy tools. To assay oligomer activity, we also demonstrate the implementation of another biophysical method involving the ratiometric imaging of Fura-2-AM loaded cells which quantifies the rate of oligomer-induced dysregulation of intracellular Ca2+ homeostasis. We anticipate that the integrated single-molecule biophysics approaches highlighted here will develop further and in principle may be extended to the investigation of other protein aggregation systems under controlled experimental conditions

Activity-regulated cytoskeleton-associated protein controls AMPAR endocytosis through a direct interaction with clathrin-adaptor protein 2

The activity-regulated cytoskeleton-associated (Arc) protein controls synaptic strength by facilitating AMPA receptor (AMPAR) endocytosis. Here we demonstrate that Arc targets AMPAR to be internalized through a direct interaction with the clathrin-adaptor protein 2 (AP-2). We show that Arc overexpression in dissociated hippocampal neurons obtained from C57BL/6 mouse reduces the density of AMPAR GluA1 subunits at the cell surface and reduces the amplitude and rectification of AMPAR-mediated miniature-EPSCs (mEPSCs). Mutations of Arc, that prevent the AP-2 interaction reduce Arc-mediated endocytosis of GluA1 and abolish the reduction in AMPAR-mediated mEPSC amplitude and rectification. Depletion of the AP-2 subunit µ2 blocks the Arc-mediated reduction in mEPSC amplitude, an effect that is restored by reintroducing µ2. The Arc-AP-2 interaction plays an important role in homeostatic synaptic scaling as the Arc-dependent decrease in mEPSC amplitude, induced by a chronic increase in neuronal activity, is inhibited by AP-2 depletion. These data provide a mechanism to explain how activity-dependent expression of Arc decisively controls the fate of AMPAR at the cell surface and modulates synaptic strength, via the direct interaction with the endocytic clathrin adaptor AP-2

Effects of thyroid status and thyrostatic drugs on hepatic glucuronidation of lodothyronines and other substrates in rats - Induction of phenol UDP-glucuronyltransferase by methimazole

Glucuronidation of iodothyronines in rat liver is catalyzed by at least three UDP-glucuronyltransferases (UGTs): bilirubin UGT, phenol UGT, and androsterone UGT. Bilirubin and phenol UGT activities are regulated by thyroid hormone, but the effect of thyroid status on hepatic glucuronidation of iodothyronines is unknown. We examined the effects of hypothyroidism induced by treatment of rats with propylthiouracil (PTU) or methimazole (MMI) or by thyroidectomy as well as the effects of T4-induced hyperthyroidism on the hepatic UGT activities for T4, T3, bilirubin, p-nitrophenol (PNP), and androsterone. Bilirubin UGT activity was increased in MMI- or PTU-induced hypothyroid and thyroidectomized rats, and decreased in hyperthyroid animals. T4 and, to a lesser extent, T3 UGT activities were increased in MMI- or PTU-induced hypothyroid rats, and T4 but not T3 glucuronidation also showed a significant increase in thyroidectomized rats. T4 but not T3 UGT activity was slightly decreased in hyperthyroid rats. While PNP UGT activity was decreased in thyroidectomized rats and increased in hyperthyroid animals, it was also markedly increased by MMI and slightly increased by PTU-induced hypothyroidism. In T4-substituted rats, MMI did not affect T4, T3, bilirubin and androsterone UGT activities but again strongly induced PNP UGT activity, indicating that this represented a direct induction of PNP UGT by the drug independent of its thyrostatic action. Androsterone UGT activity was hardly affected by thyroid status. Our results suggest a modest, negative control of the hepatic glucuronidation of thyroid hormone by thyroid status, which may be mediated by changes in bilirubin UGT activity. To our knowledge, this is the first report of the marked induction of a hepatic enzyme by MMI, which is not mediated by its thyroid hormone-lowering effect