Optimal Thresholds for Fracton Codes and Random Spin Models with Subsystem Symmetry.

Fracton models provide examples of novel gapped quantum phases of matter that host intrinsically immobile excitations and therefore lie beyond the conventional notion of topological order. Here, we calculate optimal error thresholds for quantum error correcting codes based on fracton models. By mapping the error-correction process for bit-flip and phase-flip noises into novel statistical models with Ising variables and random multibody couplings, we obtain models that exhibit an unconventional subsystem symmetry instead of a more usual global symmetry. We perform large-scale parallel tempering Monte Carlo simulations to obtain disorder-temperature phase diagrams, which are then used to predict optimal error thresholds for the corresponding fracton code. Remarkably, we found that the X-cube fracton code displays a minimum error threshold (7.5%) that is much higher than 3D topological codes such as the toric code (3.3%), or the color code (1.9%). This result, together with the predicted absence of glass order at the Nishimori line, shows great potential for fracton phases to be used as quantum memory platforms.

Increasing shade area in feedlot heifers during heat stress: physiological and performance parameters.

Heat stress is a great challenge for feedlot operations established in arid zones. The aim of this study was to evaluate if increasing shade area in the pen improved physiological and productive variables in feedlot heifers under hot climate. A total of 510 European and Zebu heifers were randomly assigned to six pens which were divided in two treatments: (1) three pens with 100 heifers each with a shade area of 2.7 m2/head (control group [C]); and (2) three pens with 70 heifers each with a shade area of 3.7 m2/head (treated group [T]). Physiological variables respiratory frequency (RF) and body surface temperature (BST) of several anatomic regions were taken from 30 heifers per treatment (i.e., 10 heifers/pen). Feed intake on pen basis was recorded weekly and heifers were individually weighted on days 1, 26, and 66 of the study to calculate performance variables. Relative humidity (RH) and ambient temperature (AT) were recorded and used to estimate the temperature-humidity index (THI). Data was analyzed with analysis of variance. The average THI during the study was 81.7 units, which was categorized as dangerous heat stress. In both shaded areas, European heifers showed higher (P < 0.05) RF than Zebu heifers. In the afternoon, the temperature of head, neck, loin, paddle, and belly was higher (P < 0.05) in C compared with T. Heifers under T showed better (P < 0.05) daily weight gain (DWG), total weight gain (TWG), feed conversion (FC), and feed efficiency (FE) than heifers in C, with no effect on dry matter intake (DMI). Results indicate that during hot summer months, Zebu showed more tolerance to heat stress than European heifers; however, heifers under a shade area of 3.7 m2/head had better productive performance than those under a shade area of 2.7 m2/head during the finishing phase of the feedlot. Increasing the shade area in the finishing phase of beef cattle on feedlot improved some physiological and productive responses during heat stress.

Consumption of seafood and its estimated heavy metals are associated with lipid profile and oxidative lipid damage on healthy adults from a Spanish Mediterranean area: A cross-sectional study.

The association between the consumption of seafood and its benefits on cardiovascular (CVD) risk can be challenged by its heavy metal (HM) content. This study aimed to explore the association of seafood consumption and its estimated HM contents with the lipid profile and lipid oxidation biomarkers in adults from a Spanish Mediterranean area who do not present risk factors for CVD. In this cross-sectional study, the clinical history, three-day dietary record, lipid profile (LDLc, HDLc, APOB/A, and triglyceride levels), plasma oxidised LDL (oxLDL) and 8-isoprostane levels of 81 adults without risk factors for CVD [43% men, with a mean age of 43.6 years (95%CI: 40.1-47.1)] were assessed. The HM [arsenic (As), cadmium (Cd), mercury (Hg), and lead (Pb)] contents of seafood were estimated according to data from analyses of marine species in the same Mediterranean area. Moderate adherence to the Mediterranean diet (score: 4.6 of 9) with a mean seafood consumption of 74.9g/day (95%CI: 59.9-89.9), including 22.7g of shellfish per day (95%CI: 13.5-31.9), was observed. The estimated HM contents were lower than the provisional tolerable weekly intakes (PTWIs): 21.12µg/kg/week As, 0.57µg/kg/week InAs, 0.15µg/kg/week Cd, 1.11µg/kg/week Hg and 0.28µg/kg/week Pb. After adjusting by confounder variables, an increase in shellfish consumption was associated with increases in the levels of LDLc (P=0.013), non-HDLc (P=0.015), APOB/A (P=0.02) and plasma oxLDL (P=0.002). Moreover, an increase in the estimated As and Hg levels in shellfish was associated with an increase in LDLc (P=0.015 and P=0.018, respectively), non-HDLc (P<0.008 and P<0.008, respectively), APOB/A ratio (P=0.008 and P=0.009, respectively), and oxLDL (P≤0.001 and P≤0.001, respectively) levels. In conclusion, in adults without risk factors for CVD, increasing shellfish consumption, even by a moderate amount, could favour a pro-atherogenic lipid profile and a higher level of oxidised LDL. These associations are likely influenced by the estimated exposure to As and Hg from shellfish despite these values are lower than the PTWIs.

Two-dimensional density-matrix topological fermionic phases: topological Uhlmann numbers.

We construct a topological invariant that classifies density matrices of symmetry-protected topological orders in two-dimensional fermionic systems. As it is constructed out of the previously introduced Uhlmann phase, we refer to it as the topological Uhlmann number n_{U}. With it, we study thermal topological phases in several two-dimensional models of topological insulators and superconductors, computing phase diagrams where the temperature T is on an equal footing with the coupling constants in the Hamiltonian. Moreover, we find novel thermal-topological transitions between two nontrivial phases in a model with high Chern numbers. At small temperatures we recover the standard topological phases as the Uhlmann number approaches to the Chern number.

Uhlmann phase as a topological measure for one-dimensional fermion systems.

We introduce the Uhlmann geometric phase as a tool to characterize symmetry-protected topological phases in one-dimensional fermion systems, such as topological insulators and superconductors. Since this phase is formulated for general mixed quantum states, it provides a way to extend topological properties to finite temperature situations. We illustrate these ideas with some paradigmatic models and find that there exists a critical temperature Tc at which the Uhlmann phase goes discontinuously and abruptly to zero. This stands as a borderline between two different topological phases as a function of the temperature. Furthermore, at small temperatures we recover the usual notion of topological phase in fermion systems.

New and Interesting Fungi. 6.

Three new genera, six new species, three combinations, six epitypes, and 25 interesting new host and / or geographical records are introduced in this study. New genera: Neoleptodontidium (based on Neoleptodontidium aquaticum), and Nothoramularia (based on Nothoramularia ragnhildianicola). New species: Acremonium aquaticum (from cooling pad water, USA, Cladophialophora laricicola (on dead wood of Larix sp., Netherlands), Cyphellophora neerlandica (on lichen on brick wall, Netherlands), Geonectria muralis (on moss growing on a wall, Netherlands), Harposporium illinoisense (from rockwool, USA), and Neoleptodontidium aquaticum (from hydroponic water, USA). New combinations: Cyphellophora deltoidea (based on Anthopsis deltoidea), Neoleptodontidium aciculare (based on Leptodontidium aciculare), and Nothoramularia ragnhildianicola (based on Ramularia ragnhildianicola). Epitypes: Cephaliophora tropica (from water, USA), Miricatena prunicola (on leaves of Prunus serotina, Netherlands), Nothoramularia ragnhildianicola (on Ragnhildiana ferruginea, parasitic on Artemisia vulgaris, Germany), Phyllosticta multicorniculata (on needles of Abietis balsamea, Canada), Thyronectria caraganae (on twigs of Caragana arborescens, Ukraine), and Trichosphaeria pilosa (on decayed Salix branch, Netherlands). Furthermore, the higher order phylogeny of three genera regarded as incertae sedis is resolved, namely Cephaliophora (Ascodesmidaceae, Pezizales), Miricatena (Helotiales, Leotiomycetes), and Trichosphaeria (Trichosphaeriaceae, Trichosphaeriales), with Trichosphaeriaceae being an older name for Plectosphaerellaceae. Citation: Crous PW, Akulov A, Balashov S, Boers J, Braun U, Castillo J, Delgado MA, Denman S, Erhard A, Gusella G, Jurjevic Z, Kruse J, Malloch DW, Osieck ER, Polizzi G, Schumacher RK, Slootweg E, Starink-Willemse M, van Iperen AL, Verkley GJM, Groenewald JZ (2023). New and Interesting Fungi. 6. Fungal Systematics and Evolution 11: 109-156. doi: 10.3114/fuse.2023.11.09.

Characteristics and treatment of nonagenarian patients with vascular disease admitted to internal medicine services. NONAVASC-2 registry.

INTRODUCTION: Vascular disease (VD) is the most frequent cause of morbidity and mortality and its prevalence increases with age. Old patients are not included in studies on VD, their characteristics and treatments being unknown. OBJECTIVE: Know the clinical characteristics of nonagenarian patients hospitalized in Internal Medicine services with a diagnosis of established VD and the adequacy of their pharmacological management. MATERIAL AND METHODS: The NONAVASC-2 registry is an observational, prospective, multicentre study. Hospitalized patients for any cause were included. Data collection was carried out through an anonymous online database with sociodemographic, clinical, analytical, therapeutic and evolutionary parameters. RESULTS: One thousand forty-nine patients with a mean age of 93.14 years (57.8% women) were included. The prevalence of risk factors and VD was high: hypertension (84.9%), dyslipidemia (50.9%) and diabetes mellitus (29.4%). 33.4% presented severe-total dependency. 82.9% received antithrombotic treatment (53.7% antiplatelets, 25.4% anticoagulation and 3.8% double therapy). Only 38.2% received statins. The percentage of severe dependence (39.2% vs 24.1%; p = 0.00) and severe cognitive impairment (30.8% vs 13.8%; p = 0.00) was significantly higher among patients who did not receive them. 19% died during admission. CONCLUSIONS: Nonagenarian patients with VD present high comorbidity, dependence and mortality. Despite being in secondary prevention, 17% did not receive antithrombotics and only 38% received statins. The underprescription is conditioned, among other factors, by the functional status. More studies are necessary to determine the impact of this issue on their prognosis.

Wilson fermions and axion electrodynamics in optical lattices.

We show that ultracold Fermi gases in optical superlattices can be used as quantum simulators of relativistic lattice fermions in 3+1 dimensions. By exploiting laser-assisted tunneling, we find an analogue of the so-called naive Dirac fermions, and thus provide a realization of the fermion doubling problem. Moreover, we show how to implement Wilson fermions, and discuss how their mass can be inverted by tuning the laser intensities. In this regime, our atomic gas corresponds to a phase of matter where Maxwell electrodynamics is replaced by axion electrodynamics: a 3D topological insulator.

Realistic time-reversal invariant topological insulators with neutral atoms.

We lay out an experiment to realize time-reversal invariant topological insulators in alkali atomic gases. We introduce an original method to synthesize a gauge field in the near field of an atom chip, which effectively mimics the effects of spin-orbit coupling and produces quantum spin-Hall states. We also propose a feasible scheme to engineer sharp boundaries where the hallmark edge states are localized. Our multiband system has a large parameter space exhibiting a variety of quantum phase transitions between topological and normal insulating phases. Because of their remarkable versatility, cold-atom systems are ideally suited to realize topological states of matter and drive the development of topological quantum computing.

Evaluation of a modified QuEChERS method for the extraction of pesticides from agricultural, ornamental and forestal soils.

A modified version of the QuEChERS method has been developed for the determination of a group of ten organophosphorus pesticides (i.e. ethoprofos, dimethoate, diazinon, malaoxon, chlorpyrifos-methyl, fenitrothion, malathion, chlorpyrifos, fenamiphos and phosmet) and one thiadiazine pesticide (buprofezin) in three different types of soils (forestal, ornamental and agricultural). The method was validated through linearity, recovery, precision and accuracy studies, and also by carrying out a matrix-matched calibration for the three soils owing to the existence of a strong matrix effect. Acceptable recovery values were obtained (between 45 and 96%) for all the pesticides and soils, except for malathion and malaoxon in forestal and ornamental soils, from which they could not be quantitatively extracted. Limits of detection of the whole method ranged between 0.48 and 7.78 ng/g. The method was finally applied to the determination of chlorpyrifos concentration in a treated soil for cultivation of potatoes.

Production, purification and characterization of serraticin A, a novel cold-active antimicrobial produced by Serratia proteamaculans 136.

AIM: This study focuses on the production, purification and characterization of serraticin A, a novel cold-active antimicrobial produced by Serratia proteamaculans 136. METHODS AND RESULTS: A Ser. proteamaculans strain producing a novel cold-active antimicrobial was isolated from Isla de los Estados, Argentina. Antimicrobial production was optimized in a BIOFLO 101 bioreactor under batch culture mode, with temperature, pH and dissolved oxygen controlled conditions. A purification protocol was developed including activated charcoal adsorption, solid-phase C18 extraction (SPE) and semi-preparative HPLC. The molecular weight was determined by LC/QTOF/MS/MS mass analysis. CONCLUSIONS: Serratia proteamaculans 136 produces a cold-active low molecular bacteriocin-like compound named serraticin A. In this work, it has been laboratory-scale produced, purified and partially characterized. Cross-immunity test revealed that serraticin A is very different from other well-known microcins assayed, with a wide inhibitory spectrum, showing an interesting biotechnology potential to be applied as a control agent against pathogenic bacteria. SIGNIFICANCE AND IMPACT OF THE STUDY: The present study is the first report of a cold-active compound with antimicrobial activity from Ser. proteamaculans. The work also highlights that cold environments could be a suitable source of micro-organisms with ability to produce cold-active biomolecules of biotechnological interest.

Treatment of primary spontaneous pneumothorax by videothoracoscopic talc pleurodesis under local anesthesia: a review of 133 procedures.

AIM: To review our experience of treatment of primary spontaneous pneumothorax by videothoracoscopic talc pleurodesis. METHODS: From 2000 to 2008, 124 consecutive patients with primary spontaneous pneumothorax were operated; 105 were men (84.7%) and 19 were women (15.3%) with a mean age of 26.6 years (range 17-46 years). RESULTS: No mortality was recorded. Staging according to Vanderschueren's classification was as follows: stage I, 61 patients (45.9%); stage II, 39 patients (29.3%); stage III, 31 patients (23.3%); stage IV, two patients (1.5%). The overall rate of complications was 9% (12/133), corresponding to prolonged air leak in 9(6.7%) patients and hemothorax in 3(2.2%) patients. Four patients (3%) had recurrence requiring reoperation. There were no episodes of acute respiratory failure, pneumonia or subcutaneous emphysema following talc pleurodesis. CONCLUSIONS: Thoracoscopic pleural talc pleurodesis as a treatment for recurrent pneumothorax is easy, safe, and rapid, and causes minimal morbidity and mortality.

Low-molecular-weight heparin dosage in newborn foals.

BACKGROUND: Heparin is used in humans as prophylaxis of hypercoagulable states and disseminated intravascular coagulation (DIC). However, babies need a higher heparin dose than do adults. Septic neonate foals are at high risk of hypercoagulable state and DIC, and there is limited objective information about heparin dose for equine neonates. OBJECTIVE: To assess whether neonate foals require higher dosages of low-molecular-weight heparin (LMWH) than adults. ANIMALS: Eighteen healthy and 11 septic neonate foals. METHODS: Experimental and clinical studies. Firstly, healthy foals were randomly distributed in 2 groups, 1 receiving 50 IU/kg SC of dalteparin and the 2nd group receiving 100 IU/kg SC of dalteparin, once daily for 3 days. Blood samples were collected before and 3, 6, 27, and 51 hours after the 1st LMWH administration. Plasma antifactor-Xa activity was measured, together with hemostatic and hematologic parameters used to assess the risk of bleeding. Subsequently, septic foals were treated blindly either with placebo (saline) or 100 IU/kg of dalteparin for 3 days. Plasma antifactor-Xa activity and other hemostatic parameters were determined before and after treatment. RESULTS: Plasma antifactor-Xa activity in healthy foals was below prophylactic activity when using the adult dosage (50 IU/kg), whereas prophylactic activities were achieved when using the double dosage (100 IU/kg). No hemorrhagic events and erythrocyte-related complications were observed with either dosage. In the clinical study, only 4/6 septic foals had plasma antifactor-Xa activity adequate for prophylaxis. CONCLUSIONS AND CLINICAL IMPORTANCE: Equine neonates require higher dosages of LMWH compared with adults to reach prophylactic heparinemia.

Association of admission plasma D-dimer concentration with diagnosis and outcome in horses with colic.

BACKGROUND: Coagulopathies detected in horses with gastrointestinal problems seem to be associated with poor outcome. Plasma D-Dimer concentration is a sensitive test for assessing coagulopathies. HYPOTHESIS: Plasma D-Dimer concentration tested on admission is related to diagnosis and outcome in horses with colic. ANIMALS: Four hundred and ninety three horses referred for evaluation of abdominal pain. METHODS: Prospective observational clinical study. Horses were grouped according to diagnosis (medical and surgical intestinal obstructions, ischemic disorders with and without intestinal resection, enteritis, peritonitis), outcome (survivors, nonsurvivors), and number of coagulopathies (normal profile, 1 or 2 coagulopathies, subclinical disseminated intravascular coagulation [DIC]). Blood samples were collected on admission and plasma D-Dimer concentration, clotting times (PT and aPTT), and antithrombin activity were determined. Positive likelihood ratios (LR+) were calculated for evaluation of D-Dimer cut-off values, which were later tested in a logistic regression model. RESULTS: Horses with enteritis or peritonitis had significantly (P<.001) higher plasma D-Dimer concentrations and more severe coagulopathies on admission than horses with other diagnoses. Nonsurvivors also had significantly (P<.001) higher plasma D-Dimer concentrations at presentation than did survivors, and those horses with subclinical DIC on presentation had an odds ratio (OR) 8.6 (95% confidence interval [CI], 3.3-22.5, P<.001) for nonsurvival. Finally, D-Dimer concentrations>4,000 ng/mL had a LR+ of 5.9 and an OR 8.8 (95% CI, 4.5-17.1, P<.001) for nonsurvival. CONCLUSION AND CLINICAL IMPORTANCE: Plasma D-Dimer concentration measured on admission can be used to facilitate diagnosis and outcome prediction in horses with colic. A potential cut-off value for nonsurvival was found at approximately 4,000 ng/mL.

[Incidence of cough after desflurane and sevoflurane administration through a laryngeal mask: a controlled clinical trial]. / Comparación de la incidencia de tos entre desflurano y sevoflurano cuando se utiliza la máscara laríngea. Ensayo clínico controlado.

OBJECTIVE: To determine the incidence of cough with the administration of desflurane and sevoflurane through a laryngeal mask. METHODS: A double-blind controlled clinical trial in 90 patients who received general anesthesia for ear, nose and throat surgery outpatient. The experimental group (n = 45) inhaled desflurane and the control group (n = 45) inhaled sevoflurane. Rugloop simulation software was used to assure that each patient was under the effect of the induction agent (propofol). The Gasman program was used to ascertain that a minimum alveolar concentration of 1 had been achieved before the hypnotic effect of propofol was lost. Cough was evaluated on the Shahbaz scale during the 10 minutes following induction and at the end of the procedure. RESULTS: Cough in the first 10 minutes was recorded in 53.6% of patients in the desflurane group and in 2.4% in the sevoflurane group (P < .05). Between-group differences were also evident at the end of surgery (desflurane group, 24%; sevoflurane group, 9.7%; P< .05). CONCLUSION: The patients who inhaled desflurane through a laryngeal mask had a higher incidence of cough than those who inhaled sevoflurane. The mechanism by which cough is being triggered by desflurane should be studied to determine whether the effect is chemical or mechanical and whether it is acting in the larynx or in the distal portion of the lung.

Effects of blood contamination on peritoneal D-dimer concentration in horses with colic.

BACKGROUND: Peritoneal D-Dimer concentration can be determined to assess peritoneal fibrinolysis activity in horses with gastrointestinal disorders. However, blood contamination of peritoneal fluid may occur during collection and could alter peritoneal D-Dimer concentration. HYPOTHESIS/OBJECTIVES: Blood contamination in peritoneal fluid does not affect interpretation of peritoneal D-Dimer concentration in horses with colic. ANIMALS: Thirty-four horses with colic and 4 healthy horses. METHODS: Peritoneal fluid and blood samples were simultaneously collected upon admission. Then, peritoneal fluid was serially contaminated with the horse's own blood; final contaminations corresponded to 1, 5, 10, and 20% of blood in peritoneal fluid. D-Dimer concentration was determined in blood, peritoneal fluid, and contaminated peritoneal fluid samples. Data were analyzed using a longitudinal linear model and a generalized estimating equations analysis to assess the quantitative and qualitative variations of the effect of blood contamination on peritoneal D-Dimer concentration. RESULTS: Peritoneal D-Dimer concentration was only quantitatively affected when peritoneal fluid was contaminated at 20% of blood. However, when using increasing cut-off values of peritoneal D-Dimer concentration (100, 2,000, 8,000, and 16,000 ng/mL), this effect disappeared at the highest cut-off values (8,000 and 16,000 ng/mL). When peritoneal fluid contamination was grouped as "minimally contaminated" (< or =1% of blood) and "highly contaminated" (> or =5% of blood), no significant differences on D-Dimer concentration between both groups at each cut-off value were observed. CONCLUSIONS AND CLINICAL IMPORTANCE: Although quantitative results of peritoneal D-Dimer concentration could be affected by high levels of blood contamination (> or =20%), interpretation of increased peritoneal fibrinolytic activity was not significantly affected.

Peritoneal D-dimer concentration for assessing peritoneal fibrinolytic activity in horses with colic.

BACKGROUND: Plasma D-dimer concentration is a useful marker to assess systemic coagulation and fibrinolytic activities in humans, dogs, and horses. Peritoneal fibrinolytic activity increases in horses with colic, especially in horses with endotoxin in the peritoneal fluid. HYPOTHESIS/OBJECTIVES: Peritoneal D-dimer concentration can be used to assess peritoneal fibrinolytic activity in horses with severe gastrointestinal (GI) disorders and altered peritoneal fluid. ANIMALS: Two hundred and twenty-one colic horses and 15 control horses. METHODS: Prospective observational clinical study. Blood and peritoneal fluid were collected on admission. Horses were grouped according to diagnosis, peritoneal fluid analysis, and outcome. Peritoneal D-dimer concentration was determined, together with peritoneal tissue-plasminogen activator (t-PA) and plasminogen activator inhibitor (PAI-1) activities. Plasma D-dimer concentration also was measured. RESULTS: Peritoneal D-dimer concentration was significantly higher in all colic groups compared with controls, and in horses with enteritis, peritonitis, and ischemic disorders compared with horses with large intestinal obstructions. Peritoneal D-dimer concentration was significantly higher in horses with altered peritoneal fluid (modified transudate and exudate) compared with horses with normal peritoneal fluid analysis. Plasma D-dimer concentration also was significantly higher in the peritonitis group, and in horses with altered peritoneal fluid analysis. Peritoneal and plasma D-dimer concentrations also were significantly higher in nonsurvivors. Peritoneal d-dimer concentration was significantly correlated with decreased peritoneal t-PA activity and increased peritoneal PAI-1 activity. CONCLUSIONS AND CLINICAL IMPORTANCE: Peritoneal D-dimer concentration is markedly higher in severe GI disorders, and it can be used to assess peritoneal fibrinolytic activity in horses with colic.

Absorbed dose profiles for (32)P, (90)Y, (188)Re, (177)Lu, (153)Sm and (169)Er: radionuclides used in radiosynoviortheses treatment.

The main objective of this paper was to obtain the absorbed dose profiles for radionuclides of frequent or potential use in radiosynoviortheses. These profiles reveal the absorbed dose per activity of injected radionuclide (Gy/h*MBq) in the synovial membrane and the articular cartilage. The researched radionuclides were (32)P, (90)Y, (188)Re, (177)Lu, (153)Sm and (169)Er. The therapeutic range of each radionuclides in synovial tissue were also calculated. This range determines the synovial thickness that can be sufficiently irradiated and thus successfully treated. The S values for the synovial membrane and articular cartilage were calculated using as a model a cylinder with the source uniformly distributed in its volume. The synovial membrane was simulated varying the radius of the cylinder (from 0.5cm to 9cm) and its height (from 0.01cm to 0.04cm). The area in the base of the cylinder represents different sizes of the synovial surface (small, medium and large joints). The height of the cylinder represents different stages of the progression of the rheumatoid arthritis. The same model was used to simulate the articular cartilage but, the source was uniformly distributed into a cylindrical slab (0.01cm height and 1cm of radius. The results obtained allow the estimation of the dose that will be delivered to the synovial membrane and the articular cartilage for different joint sizes and different stages of progression of the rheumatoid arthritis (RA).

Rheology of epoxidized cellulose pulp gel-like dispersions in castor oil: Influence of epoxidation degree and the epoxide chemical structure.

Several di- or tri-functional epoxides were used to chemically modify an industrial grade cellulose pulp from Eucalyptus globulus in order to thicken castor oil by dispersing epoxidized cellulose pulp fibers, resulting gel-like formulations with potential applications as biolubricants. Rheological properties of these colloidal suspensions were evaluated by analysing the effects of epoxidation degree and the epoxide chemical structure. With this aim, epoxidized cellulose pulp samples were characterized by means of epoxy index determination, thermogravimetric analysis (TGA) and Fourier transform infrared (FTIR) spectroscopy. It was found that linear viscoelastic functions, determined in small-amplitude oscillatory shear (SAOS), and viscosity values of epoxidized cellulose pulp gel-like dispersions decreased by increasing the epoxy index, whereas the shear-thinning character was dampened with the extension of epoxidation. Aromatic di-functional epoxides provide higher values of these rheological functions than aliphatic ones.