6th San Luis Conference on Surfaces,Interfaces and Catalysis

Topics in Catalysis -     

Kinetic and thermodynamic study of thermal inactivation of the antimicrobial peptide P34 in milk

The knowledge on thermal inactivation of biopreservatives in a food matrix is essential to allow their proper utilisation in food industry, enabling the reduction of heating times and optimisation of heating temperatures. In this work, thermal inactivation of the antimicrobial peptide P34 in skimmed and fat milk was kinetically investigated within the temperature range of 90–120 °C. The inactivation kinetic follows a first-order reaction with k-values between 0.071 and 0.007 min⁻¹ in skimmed milk, and 0.1346 and 0.0119 min⁻¹ in fat milk. At high temperatures, peptide P34 was less resistant in fat milk, with a significant decrease in residual activity as compared with skimmed milk. At temperatures below 110 °C, the fat globules seem to have protective effect to the peptide P34. Results suggest that peptide P34 is heat stable in milk with activation energy of 90 kJ mol⁻¹ in skimmed milk and 136 kJ mol⁻¹ in fat milk.     

Early harvest of monsoon rice to address seasonal hunger in northwest Bangladesh

Bangladesh has a high global hunger index with grave impacts of seasonal hunger. Short duration varieties (SDV) and direct seeding of rice (DSR) were introduced to farmers in NW Bangladesh during the monsoon season or kharif-2 to overcome seasonal hunger or monga. These technology options allow early harvest, which increased household food security and livelihood opportunities during and beyond the hunger season. The farmers who used short duration varieties and/or direct seeding were able to harvest three weeks earlier than those who used the traditional practice of long duration varieties and transplanting. More than 70 % of the SDV_DSR farmers completed harvest by mid-October, and all had done so by the end of October, whereas fewer than 5 % of farmers who grew long duration rice varieties that were transplanted, had harvested within the monga period, with most of them (80 %) harvesting during the last week of November. Early harvesting of rice generated significant, multifaceted impacts on the lives of rice farming communities in northwest Bangladesh by increasing rice production, and providing and/or increasing income along with creating additional jobs for the landless or agriculture day laborers in the lean or monga period. We estimated that during the monsoon season, the average hired labor demand was 40 person days/ha, with around 67 % of this labor generated by SDV_DSR. Further, there were improvements in access and availability of food during deficit times of the year. These technology options for rice production could be scaled out in similar agro-environments to reduce seasonal hunger and produce positive benefits on a range of factors.     

Influence of ligand structure and water interactions on the physical properties of β-cyclodextrins complexes

The water sorption and physical properties of freeze-dried β-cyclodextrin (BCD) and 2-hydroxypropyl-β-cyclodextrin (HBCD) were studied. The stability of the inclusion complexes of these cyclodextrins with different hydrophobic ingredients, such as myristic acid and α-terpineol, was investigated as a function of the storage time and water content of the systems. Besides increasing its solubility, BCD ring modification with hydroxypropyl groups conferred amorficity to the dehydrated matrices, and modified the sorption properties and their ability to form hydrates.     

Control of spatial orientation in terrestrial toads (Rhinella arenarum).

Three experiments were conducted to determine problem-solving strategies used by toads, Rhinella arenarum (= Bufo arenarum), in spatial learning situations, using water as reward. Experiment 1 showed that toads can acquire a spatial orientation based on a body-centered turn -an internal self-reference cue. Experiment 2 showed that toads can use a fixed landmark (visual cue) as guidance to solve a spatial problem. Experiment 3 determined whether maze learning was based on “body-centered turn” or “guidance”. In this case, animals were trained with a fixed visual cue in relation to a body-centered turn (i.e., simultaneously with the internal self-reference cue) and then tested with the visual cue dissociated from positional cues. Toads trained with the combination of a visual cue and a body-centered turn preferred the latter (turn response) when the two sources of information were set in conflict on probe trials. Toads showed behavioral patterns similar to those described in rodents trained under similar condition, thus, suggesting an early evolutionary origin for these problem-solving strategies. (PsycINFO Database Record (c) 2011 APA, all rights reserved)     

Comments on: A random forest guided tour

This paper is a comment on the survey paper by Biau and Scornet (TEST, 2016. doi: 10.1007/s11749-016-0481-7) about random forests. We focus on the problem of quantifying the impact of each ingredient of random forests on their performance. We show that such a quantification is possible for a simple pure forest, leading to conclusions that could apply more generally. Then, we consider “hold-out” random forests, which are a good middle point between “toy” pure forests and Breiman’s original random forests.     

Effects of sintering temperature on morphology and mechanical characteristics of 3D printed porous titanium used as dental implant

Porous titanium samples were manufactured using the 3D printing and sintering method in order to determine the effects of final sintering temperature on morphology and mechanical properties. Cylindrical samples were printed and split into groups according to a final sintering temperature (FST). Irregular geometry samples were also printed and split into groups according to their FST. The cylindrical samples were used to determine part shrinkage, in compressive tests to provide stress-strain data, in microCT scans to provide internal morphology data and for optical microscopy to determine surface morphology. All of the samples were used in microhardness testing to establish the hardness. Below 1100 °C FST, shrinkage was in the region of 20% but increased to approximately 30% by a FST of 1300 °C. Porosity varied from a maximum of approximately 65% at the surface to the region of 30% internally. Between 97 and 99% of the internal porosity is interconnected. Average pore size varied between 24 μm at the surface and 19 μm internally. Sample hardness increased to in excess of 300 HV0.05 with increasing FST while samples with an FST of below 1250 °C produced an elastic–brittle stress/strain curve and samples above this displayed elastic–plastic behaviour. Yield strength increased significantly through the range of sintering temperatures while the Young's modulus remained fairly consistent.     

Performing organic chemistry with inorganic compounds: electrophilic reactivity of selected nitrosyl complexes

The inorganic nitrosyl (NO(+)) complexes [Fe(CN) 5NO](2-), [Ru(bpy)2(NO)Cl](2+), and [IrCl 5(NO)](-) are useful reagents for the nitrosation of a variety of organic compounds, ranging from amines to the relatively inert alkenes. Regarding [IrCl 5(NO)](-), its high electrophilicity and inertness define it as a unique reagent and provide a powerful synthetic route for the isolation and stabilization of coordinated nitroso compounds that are unstable in free form, such as S-nitrosothiols and primary nitrosamines. Related to the high electrophilicity of [IrCl 5(NO)](-), an unusual behavior is described for its PPh 4(+) salt in the solid state, showing an electronic distribution represented by Ir(IV)-NO(*) instead of Ir (III)-NO(+) (as for the K(+) and Na(+) salts).     

Retinal Toxicity Induced by Chemical Agents

Vision is an important sense for humans, and visual impairment/blindness has a huge impact in daily life. The retina is a nervous tissue that is essential for visual processing since it possesses light sensors (photoreceptors) and performs a pre-processing of visual information. Thus, retinal cell dysfunction or degeneration affects visual ability and several general aspects of the day-to-day of a person’s lives. The retina has a blood–retinal barrier, which protects the tissue from a wide range of molecules or microorganisms. However, several agents, coming from systemic pathways, reach the retina and influence its function and survival. Pesticides are still used worldwide for agriculture, contaminating food with substances that could reach the retina. Natural products have also been used for therapeutic purposes and are another group of substances that can get to the retina. Finally, a wide number of medicines administered for different diseases can also affect the retina. The present review aimed to gather recent information about the hazard of these products to the retina, which could be used to encourage the search for more healthy, suitable, or less risky agents.