Characterization of the hierarchical architecture and micromechanical properties of walnut shell (Juglans regia L.).

In the present work a comprehensive characterization of the hierarchical architecture of the walnut shell (Juglans regia L.) was carried out using scanning electron microscopy (SEM), atomic force microscopy (AFM) and confocal laser scanning microscopy (CLSM). Furthermore, micromechanical properties (hardness, HIT and elastic modulus, EIT) of plant tissues were evaluated at cell wall level by applying the instrumented indentation technique (IIT). The complex architecture of the material was described in terms of four hierarchical levels (HL): endocarp (H1), plant tissues (H2), plant cells (H3) and cell wall (H4). Our findings revealed that the walnut shell consists of a multilayer structure (sclerenchyma tissue, ST; interface tissue, IT; porous tissue, PT; and flattened parenchyma tissue, FPT), where differences in the microstructure and composition of plant tissues generate parallel gradients along the cross-section. The indentation tests showed a functional gradient with a sandwich-like configuration, i.e., a lightweight and soft layer (PT, HIT = 0.04 GPa) is located between two dense and hard layers (ST, HIT = 0.33 GPa; FPT, HIT = 0.28 GPa); where additionally there is an interface between ST and PT (IT, HIT = 0.16 GPa). This configuration is a successful strategy designed by nature to improve the protection of the kernel by increasing the strength of the shell. Therefore, the walnut shell can be considered as a functionally graded material (FGM), which can be used as bioinspiration for the design of new functional synthetic materials. In addition, we proposed some structure-property-function relationships in the whole walnut shell and in each of the plant tissues.

Effect of calcium oxalate crystals on the micromechanical properties of sclerenchyma tissue from the pecan nutshell (Carya illinoinensis).

The objective of this study was to evaluate the effect of the presence of calcium oxalate (CaOx) crystals on the micromechanical properties of sclerenchyma tissue from the pecan nutshell (Carya illinoinensis). The microstructure of the cross-section nutshell was examined using light microscopy (LM) and atomic force microscopy (AFM). Using an instrumented indentation system, indentation tests with maximum loads of 500 mN were made on the biological material where the variables studied were the number of crystals present in the evaluated area and the size of individual crystals. Microscopic analysis revealed that the pecan nutshell consists of sclerenchyma tissue with multiple CaOx crystals randomly distributed throughout the material, exhibiting prismatic shapes and various sizes. The results of the indentation tests showed that the examined areas where there were crystals (1, 2 or up to 3) presented values of hardness and elastic modulus significantly higher (P < 0.05) compared to the sclerenchyma (without crystals). Likewise, there were no significant differences (P > 0.05) between the values of the micromechanical properties of the areas evaluated as a function of the number of crystals. On the other hand, it was observed that the size of the crystals did not show a direct correlation with the mechanical properties evaluated as expected. In conclusion, the biomineralization phenomenon is a successful strategy designed by nature to improve the rigidity of the pecan nutshell, where the CaOx crystals strengthen the structure by increasing the micromechanical properties.

Riesgo de hipocalcemia aguda en paciente hipoparatiroidea postiroidectomía que practica ejercicio de resistencia: a próposito de un caso / Risk of acute hypocalcaemia in a patient after total thyroidectomy and during endurance exercise: A case report

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Procalcitonin and C-reactive protein as early markers of postoperative intra-abdominal infection in patients operated on colorectal cancer.

PURPOSE: The aim of this study was to evaluate the accuracy of serum procalcitonin (PCT) and C-reactive protein (CRP) for early diagnosis of postoperative intra-abdominal infections (PIAI) after elective surgery for colorectal cancer. METHODS: Prospective observational study including patients operated on for colorectal cancer between January and December of 2015 was performed. Serum PCT and CRP levels were measured before surgery and daily until postoperative day 3. RESULTS: One hundred twenty patients were included. Seven patients (5.8%) had PIAI. PCT levels were significantly higher in patients with PIAI on postoperative days 1 and 3, whereas CRP levels only were significantly more elevated on postoperative day 3. The ratio between CRP levels on postoperative day 3 and CRP levels on postoperative days 2 (CRP D3/CRP D2) and 1 (CRP D3/CRP D1) was significantly higher in patients with PIAI. PCT on postoperative day 3, for a cutoff of 0.45 ng/mL, had the best sensitivity (100%) with a specificity of 73.8%. The ratio CRP D3/CRP D1 yielded the higher specificity and positive predictive value (90.9 and 27.3%, respectively, for a cutoff of 1.8). The higher negative predictive value was obtained for PCT on postoperative days 1 and 3 (100%, with cutoff of 0.76 and 0.45 ng/mL, respectively) and for CRP on postoperative day 3 (100% with cutoff of 10 mg/dL). CONCLUSION: PCT and CRP serum levels are associated with the appearance of PIAI after colorectal cancer surgery, although the positive predictive values were low for both PCT and CRP. However, the negative predictive values were high.