Hematite mining in the ancient Americas: Mina Primavera,A 2,000 year old Peruvian mine

Mina Primavera, a hematite (Fe₂O₃) mine located in southern Peru, was exploited beginning approximately 2,000 years ago by two Andean civilizations, the Nasca and Wari. Despite the importance of hematite in the material culture of the ancient Americas, few hematite mines have been reported in the New World literature and none have been reported for the Central Andes. An estimated 3,710 tonnes of hematite were extracted from the mine for over 1,400 years at an average rate of 2.65 tonnes per year, suggesting regular and extensive mining prior to Spanish conquest. The hematite was likely used as a pigment for painting pottery, and the mine demonstrates that iron ores were extracted extensively at an early date in the Americas.     

Efficacy of embryo transfer in lactating dairy cows during summer using fresh or vitrified embryos produced in vitro with sex-sorted semen

The objective was to determine whether transfer of fresh or vitrified embryos produced in vitro with sex-sorted semen improves pregnancy and calving rates during summer in lactating dairy cows compared with artificial insemination (AI). Lactating dairy cows (n = 722) were enrolled during summer months at 2 commercial dairies in Central Texas and randomly assigned to 1 of 3 treatments: AI with conventional semen (n = 227), embryo transfer-vitrified (ET-V; n = 279) or embryo transfer-fresh (ET-F; n = 216). Embryos were produced in vitro using sex-sorted semen and with Block-Bonilla-Hansen-7 culture medium. For vitrification, grade 1 expanded blastocysts were harvested on d 7 after fertilization and vitrified using the open-pulled straw method. Fresh embryos were grade 1 blastocysts and expanded blastocysts harvested on d 7 after fertilization. Cows were submitted to the Ovsynch56 protocol: d −10 GnRH, d −3 PGF_2α, d −1 GnRH and d 0 timed AI; or Select Synch protocol: d −9 GnRH, d −2 PGF_2α, and AI following detected estrus (day of AI = d 0). On d 7, all cows were examined for presence of a corpus luteum (CL). A vitrified or fresh embryo was transferred to cows with CL in ET-V and ET-F groups. Cows were considered synchronized if progesterone was <1 ng/mL on d 0 and a CL was present on d 7. At d 40 ± 7 of gestation, the percentage of cows pregnant was greater for the ET-F compared with the ET-V and AI groups among all cows (42.1 vs. 29.3 and 18.3%, respectively) and synchronized cows (45.5 vs. 31.6 and 24.8%, respectively). Also, the percentage of cows pregnant was greater for the ET-V than the AI group among all cows and tended to be greater among synchronized cows. At d 97 ± 7 of gestation, the percentage of cows pregnant among all cows was greater for ET-F and ET-V groups than for the AI group (36.4 and 25.7 vs. 17.0%, respectively) and the percentage for the ET-F group was greater than for the ET-V group. Among synchronized cows, the percentage of cows pregnant was significantly increased for the ET-F group than for ET-V and AI groups (39.4 vs. 27.8 and 23.1%, respectively) and no difference was found between ET-V and AI groups. No effect of treatment on embryo loss was observed. The percentage of cows with live births was significantly increased for the ET-F than for ET-V and AI groups among all cows (27.5 vs. 17.1 and 14.6%, respectively) and synchronized cows (29.9 vs. 18.5 and 20.0%, respectively). The percentage of cows giving birth to a live heifer was significantly increased for the ET-F and ET-V groups compared with the AI group among all cows (79.1 and 72.5 vs. 50.0%, respectively) and synchronized cows (79.1 and 72.5 vs. 50.0%, respectively). No difference existed between ET-F and ET-V groups for percent live heifer births but both were greater than for the AI group. The transfer of fresh embryos produced in vitro using sex-sorted semen to lactating dairy cows during summer can effectively increase the percentage of cows that establish pregnancy and also the percentage of cows that give birth to a live heifer compared with percentages from AI with conventional semen.     

Fullerene Desymmetrization as a Means to Achieve Single‐Enantiomer Electron Acceptors with Maximized Chiroptical Responsiveness

Solubilized fullerene derivatives have revolutionized the development of organic photovoltaic devices, acting as excellent electron acceptors. The addition of solubilizing addends to the fullerene cage results in a large number of isomers, which are generally employed as isomeric mixtures. Moreover, a significant number of these isomers are chiral, which further adds to the isomeric complexity. The opportunities presented by single‐isomer, and particularly single‐enantiomer, fullerenes in organic electronic materials and devices are poorly understood however. Here, ten pairs of enantiomers are separated from the 19 structural isomers of bis[60]phenyl‐C61‐butyric acid methyl ester, using them to elucidate important chiroptical relationships and demonstrating their application to a circularly polarized light (CPL)‐detecting device. Larger chiroptical responses are found, occurring through the inherent chirality of the fullerene. When used in a single‐enantiomer organic field‐effect transistor, the potential to discriminate CPL with a fast light response time and with a very high photocurrent dissymmetry factor (g_ph = 1.27 ± 0.06) is demonstrated. This study thus provides key strategies to design fullerenes with large chiroptical responses for use as chiral components of organic electronic devices. It is anticipated that this data will position chiral fullerenes as an exciting material class for the growing field of chiral electronic technologies.