Glacial-postglacial temperature difference deduced from aspartic Acid racemization in fossil bones

The magnitude of the temperature increase that occurred in continental regions following the termination of the last glaciation has been determined from the degree of racemization of aspartic acid in fossil bones of known age. The results indicate an increase of 4 degrees C for the Mediterranean coast and 5 degrees to 6 degrees C for East Africa. These estimates are believed to be reliable within 1 degrees C.     

The Miller volcanic spark discharge experiment

Miller's 1950s experiments used, besides the apparatus known in textbooks, one that generated a hot water mist in the spark flask, simulating a water vapor-rich volcanic eruption. We found the original extracts of this experiment in Miller's material and reanalyzed them. The volcanic apparatus produced a wider variety of amino acids than the classic one. Release of reduced gases in volcanic eruptions accompanied by lightning could have been common on the early Earth. Prebiotic compounds synthesized in these environments could have locally accumulated, where they could have undergone further processing.     

Feline hip joint anatomy in magnetic resonance images

The aim of this study was to develop an anatomical model of the feline hip joint for low‐field magnetic resonance imaging (LF‐MRI) based on high‐field magnetic resonance imaging (HF‐MRI). The study was performed on six adult clinically healthy European shorthair cats, aged 1–3 years, with body weight of 2.8–4.4 kg. The animals were examined with the use of the Vet‐MRI Grande Esaote LF (0.25 T) scanner and high‐field Siemens Magnetom TRIO (3 T) MRI scanner. In the LF‐MRI, most satisfactory results in T1‐weighted images were obtained when TE was 26 ms in all three planes and when TR was 350–950 ms in the transverse plane, 950–1150 ms in the sagittal plane and 520–750 ms in the dorsal plane. In T2‐weighted images, TE was 90 ms in the transverse and dorsal plane and 120 ms in the sagittal plane. The results were presented as images acquired with LF‐MRI scanners in three planes. The slice thickness was 3 mm for each plane. In LF‐MRI, muscles in the hip joint region and round ligament were well visualized. Unlike in LF‐MRI, the cross section of the femoral nerve was identified in HF‐MRI scans. In examinations of the feline hip joint, the main limitations of LF‐MRI were a lack of reliable contrast between articular cartilage and synovial fluid as well as longer scan time. Despite the above, LF‐MRI images were characterized by good contrast between bones and the surrounding soft tissues.     

Fishery indicators during a predictable aggregation of Atlantic sharpnose sharks Rhizoprionodon terraenovae in the southern Gulf of Mexico: An alternative to assess a heterogeneous data‐poor fishery

Small‐scale fisheries in the southern Gulf of Mexico that catch Rhizoprionodon terraenovae (Richardson) are heterogeneous and data‐poor. Fishery‐dependent monitoring was conducted from 2010 to 2017, including a target season during an aggregation of this species to estimate data‐poor fishery indicators. During the target season, the average sizes for females and males (95.3 and 89.8 cm total length, respectively) were recorded, a global male sex bias (1:1.7), the highest percentage of mature sharks for all years (>89%), the highest values of CPUE (20.1 sharks/day) and size‐selectivity higher than the size at maturity. The spawning potential ratio was over 0.6 (reference point of 0.71) in the combined (target and non‐target) and target seasons for all years, which suggests that the fishery stock is not healthy. Annual assessment of this fishery can be carried out through monitoring during the target season, where management is more feasible to implement.     

Application of two-step laser mass spectrometry to cosmogeochemistry: direct analysis of meteorites

Polycyclic aromatic hydrocarbons in C1, C2, and C3 carbonaceous chondrites and in some ordinary chondrites have been directly analyzed by two-step laser desorption/ laser multiphoton ionization mass spectrometry, a selective and sensitive method requiring only milligram samples. At the ionization wavelength of 266 nanometers, parent ion peaks of polycyclic aromatic hydrocarbons dominate the mass spectra. Quantitative analysis is possible; as an example, the concentration of phenanthrene in the Murchison meteorite was determined to be 5.0 parts per million.