Effect of Calcination Temperature and Chemical Composition of PAN-Derived Carbon Microfibers on N2, CO2, and CH4 Adsorption.

This work investigates the interplay of carbonization temperature and the chemical composition of carbon microfibers (CMFs), and their impact on the equilibration time and adsorption of three molecules (N2, CO2, and CH4). PAN derived CMFs were synthesized by electrospinning and calcined at three distinct temperatures (600, 700 and 800 °C), which led to samples with different textural and chemical properties assessed by FTIR, TGA/DTA, XRD, Raman, TEM, XPS, and N2 adsorption. We examine why samples calcined at low/moderate temperatures (600 and 700 °C) show an open hysteresis loop in nitrogen adsorption/desorption isotherms at -196.15 °C. The equilibrium time in adsorption measurements is nearly the same for these samples, despite their distinct chemical compositions. Increasing the equilibrium time did not allow for the closure of the hysteresis loop, but by rising the analysis temperature this was achieved. By means of the isosteric enthalpy of adsorption measurements and ab initio calculations, adsorbent/adsorbate interactions for CO2, CH4 and N2 were found to be inversely proportional to the temperature of carbonization of the samples (CMF-600 > CMF-700 > CMF-800). The enhancement of adsorbent/adsorbate interaction at lower carbonization temperatures is directly related to the presence of nitrogen and oxygen functional groups on the surface of CMFs. Nonetheless, a higher concentration of heteroatoms also causes: (i) a reduction in the adsorption capacity of CO2 and CH4 and (ii) open hysteresis loops in N2 adsorption at cryogenic temperatures. Therefore, the calcination of PAN derived microfibers at temperatures above 800 °C is recommended, which results in materials with suitable micropore volume and a low content of surface heteroatoms, leading to high CO2 uptake while keeping acceptable selectivity with regards to CH4 and moderate adsorption enthalpies.

Effects of different equilibration times at 5 °C on boar sperm cryotolerance.

Equilibration time (ET) is the period during which sperm cells are in contact with cooling/freezing media components at a temperature of 5 °C, providing a proper osmotic balance between the intra- and extra-cellular milieu. The present study aimed to determine the ET (0, 2, and 4 h) that results in greater post-thaw sperm quality and functions. Based on the post-thaw sperm membrane integrity and motility ratios, 20 ejaculates collected from five boars were classified as having good (GFE, n = 5) or poor (PFE, n = 15) freezing capacity. Ratios of post-thaw sperm with intact plasma membrane and acrosome were similar between ET (0 h: 37.02 % ± 2.85 %; 2 h: 34.59 % ± 7.12 %; 4 h: 37.87 % ± 4.44 %) in GFE samples. In PFE, ratios of sperm with intact plasma membrane and acrosome at post-thaw were greater (P < 0.05) after an ET of 2 h than after an ET of 0 h (2 h: 26.16 % ± 1.54 % and 0 h: 16.74 % ± 1.59 %). Also, ratios of post-thaw sperm with relatively lesser membrane lipids disorder were greater (P < 0.05) after an ET of 2 h than for other ET in both GFE (2 h: 21.97 % ± 4.24 % and 0 h: 16.63 % ± 2.38 %) and PFE (2 h: 16.65 % ± 1.40 % and 0 h: 13.23 % ± 1.25 %) samples. In conclusion, an ET of 2 h results in greater sperm cryotolerance in both GFE and PFE samples, which suggests that modifying the freezing protocol lead to an increase post-thaw sperm function and survival.

Influência do tempo de equilíbrio sobre a qualidade do sêmen caprino após a descongelação / Influence of balance time on quality of buck semen after thawing

The animals were divided into three groups G1, G2, G3. Semen collected was diluted in Tris-yolk baseand packaged in 0.25 ml straws, a dose of 100 x 106 sperm. Semen samples were distributed in differentequilibrium time protocols. The group 1 (1h), group 2 (2 h), group 3 (3 h). Mean values for motility were19.37%, 16.87% and 16.25% respectively for G1, G2 and G3. To analyze (TTR) which consisted of placing asemen , and incubated at 37°C for a period of 120 minutes. The force sperm motility and sperm were evaluatedby TTR in different time: 0, 60, 120, 180 minutes. The indices obtained from motility and sperm vigor wereevaluated by PROC GLM (SAS, 2001) and proceeded to the 5% Tukey test. This study demonstrated effect theequilibration period, on the viability of goat semen after the freeze-thaw process, in which the semen exposed toless cooling time has a higher sperm viability.(AU)

Influência do tempo de equilíbrio sobre a qualidade do sêmen caprino após a descongelação / Influence of balance time on quality of buck semen after thawing

The animals were divided into three groups G1, G2, G3. Semen collected was diluted in Tris-yolk baseand packaged in 0.25 ml straws, a dose of 100 x 106 sperm. Semen samples were distributed in differentequilibrium time protocols. The group 1 (1h), group 2 (2 h), group 3 (3 h). Mean values for motility were19.37%, 16.87% and 16.25% respectively for G1, G2 and G3. To analyze (TTR) which consisted of placing asemen , and incubated at 37°C for a period of 120 minutes. The force sperm motility and sperm were evaluatedby TTR in different time: 0, 60, 120, 180 minutes. The indices obtained from motility and sperm vigor wereevaluated by PROC GLM (SAS, 2001) and proceeded to the 5% Tukey test. This study demonstrated effect theequilibration period, on the viability of goat semen after the freeze-thaw process, in which the semen exposed toless cooling time has a higher sperm viability.

Influence of catalase and pre-freezing equilibration on post-thaw semen quality and conception rate in ewes laparoscopically inseminated

The aim of this study was to investigate the effects of catalase and pre-freezing equilibration during ram sperm cryopreservation on motility and membrane and acrosomal integrity of frozen-thawed semen, as well as conception rate following laparoscopic timedinsemination. Semen was collected from four mature Dorper rams, pooled and diluted in Tris egg-yolk extender basic solution (CON), or this solution supplemented with catalase (CAT; 20 U/100 × 106 sperm). Extended semen was packaged in 0.25 ml mini straws (25 × 106 sperm/straw), chilled (to 5°C), and then either frozen immediately (CON and CAT) or maintained at 5°C for 12 h of pre-freezing equilibration (CON12 and CAT12). Immediately after thawing and at 1 h after incubation at 37°C, kinematic parameters (CASA), plasma membrane integrity (PI-FITC), and acrosomal status (FITC-PNA) of sperm were assessed. There were no significant differences among the four groups on sperm traits evaluated immediately postthaw. However, after 1 h of incubation, total motility (46.7 and 25.0%) and plasma membrane integrity (38.7 and 25.7%) were higher (P < 0.05) in CAT12 than CON. When these two treatments were used for laparoscopic timed artificial insemination of ewes (with synchronized ovulation), conception rate was similar for CAT12 and CON (32.8%, n = 61 vs. 27.3%, n = 55). In conclusion, the combination of catalase and pre-freezing equilibration resulted in significantly improved quality of post-thawed ram semen without affecting conception rate in fixed-time laparoscopically intrauterine inseminated ewes.(AU)

Influence of catalase and pre-freezing equilibration on post-thaw semen quality and conception rate in ewes laparoscopically inseminated

The aim of this study was to investigate the effects of catalase and pre-freezing equilibration during ram sperm cryopreservation on motility and membrane and acrosomal integrity of frozen-thawed semen, as well as conception rate following laparoscopic timedinsemination. Semen was collected from four mature Dorper rams, pooled and diluted in Tris egg-yolk extender basic solution (CON), or this solution supplemented with catalase (CAT; 20 U/100 × 106 sperm). Extended semen was packaged in 0.25 ml mini straws (25 × 106 sperm/straw), chilled (to 5°C), and then either frozen immediately (CON and CAT) or maintained at 5°C for 12 h of pre-freezing equilibration (CON12 and CAT12). Immediately after thawing and at 1 h after incubation at 37°C, kinematic parameters (CASA), plasma membrane integrity (PI-FITC), and acrosomal status (FITC-PNA) of sperm were assessed. There were no significant differences among the four groups on sperm traits evaluated immediately postthaw. However, after 1 h of incubation, total motility (46.7 and 25.0%) and plasma membrane integrity (38.7 and 25.7%) were higher (P < 0.05) in CAT12 than CON. When these two treatments were used for laparoscopic timed artificial insemination of ewes (with synchronized ovulation), conception rate was similar for CAT12 and CON (32.8%, n = 61 vs. 27.3%, n = 55). In conclusion, the combination of catalase and pre-freezing equilibration resulted in significantly improved quality of post-thawed ram semen without affecting conception rate in fixed-time laparoscopically intrauterine inseminated ewes.