Martian orbital and lander measurements revealed strong (∼1–2 orders of magnitude greater than Earth) crustal magnetic anomalies and the lack of an active detectable core dynamo. This strong crustal ...magnetization remains unexplained given that models of an ancient core dynamo on Mars predict surface field strengths comparable to modern Earth. We explored the relationship between Mars' crustal magnetization and its composition in multivariate space. We identified that 530 and 1,000 nm absorptions (from orbital spectrometers) have unique correlations with crustal magnetization in the Terra Sirenum‐Terra Cimmeria region and ∼13% of the variance of the magnetization can be attributed to these correlations. Because we do not expect the topmost material, detectable by the orbital spectrometers, to retain magnetization from an ancient core dynamo, we propose this material is compositionally similar to the bulk rock below it, which is more likely to retain magnetization. Therefore, the observed variance is a lower limit.
Plain Language Summary
Currently Mars has no global magnetic field. However, at some point it did have a global magnetic field. Instruments from past missions have spotted patches on Mars' surface that are strongly magnetized. This can be explained by the fact that the crust was formed during a time when the global magnetic field was present, and so it locked in on that magnetic field. Previous models suggest that when Mars' global magnetic field was present, it was approximately of the same strength as Earth's current field. A magnetic field of this strength would not have produced such a strongly magnetized crust. Therefore, the magnetization strength of those patches is a mystery. We explored the relationships between the strength of the magnetic field on the surface and the composition of the crust. Our findings show that in the area with the strongest magnetic patches, there is a verifiable positive correlation between the magnetic field and mineralogical data. This leads us to believe that the composition of those patches enables them to record the magnetic field exceptionally well. Therefore, Mars' ancient global magnetic field did not need to be anomalously large to produce the strongly magnetized crust we observe.
Key Points
The strong magnetization observed in the Terra Sirenum‐Terra Cimmeria region is at least partially due to compositional enhancement
The Terra Sirenum‐Terra Cimmeria region has not experienced widespread demagnetization processes since formation
The magnetization in the Terra Sirenum‐Terra Cimmeria region is carried in the bulk rock with representative materials exposed at the surface
Observations of planetary magnetic fields provide fundamental insights into the origin and evolution of terrestrial planets. However, whether Venus ever hosted a dynamo is unknown. Here we show that ...crustal remanent magnetism is a potentially observable consequence of an ancient Venusian dynamo, in contrast to previous studies that dismissed this possibility. Past spacecraft measurements only exclude crustal magnetization near the Venera 4 landing site and northward of 50° South latitude for >150‐km coherence scales and strong magnetization intensities. Magnetite grains with sizes commonly observed in volcanic rocks can retain thermoremanent magnetism at Venusian conditions for >1 billion years. Depths to the Curie temperature of magnetite are ~5–40 km and typically less than predicted crustal thicknesses at our analyzed localities. Aerial platforms could detect expected magnetizations at horizontal scales similar to the ~50‐km operating altitude. Any detection would validate models of planetary accretion, geologic processes, and climate history.
Plain Language Summary
Unlike Earth, Venus has no global magnetic field generated by churning fluid in its metallic core. Models indicate that Venus may have hosted an Earth‐strength field until at least a billion years ago—roughly the average surface age—if giant impacts mixed the core during planetary formation. Without energetic impacts, models suggest that chemical layering in the core would always suppress fluid motions and thus a dynamo. Searching for ancient magnetized rocks (already discovered on Moon, Mars, and Mercury) would test these models. Venus has a very hot surface, which decreases the stability of ancient magnetization and has caused pessimism about the chances of obtaining useful data. However, we found that common minerals such as magnetite are magnetically stable for billions of years at the current surface temperature. Enough crust could remain magnetized to produce signals detectable by orbiters at low altitudes or, ideally, aerial platforms floating in the atmosphere.
Key Points
Whether Venus once hosted a dynamo‐generated magnetic field has broad implications for the accretion and evolution of terrestrial planets
Despite high surface temperatures on Venus, magnetite and hematite grains may retain thermoremanent magnetization for >1 billion years
Crust magnetized to depths of >1‐5 km could produce signals detectable by an aerial platform operating at ~50‐km altitude
The Mastcam-Z Camera is a stereoscopic, multispectral camera with zoom capability on NASA’s Mars-2020
Perseverance
rover. The Mastcam-Z relies on a set of two deck-mounted radiometric calibration ...targets to validate camera performance and to provide an instantaneous estimate of local irradiance and allow conversion of image data to units of reflectance (R
∗
or I/F) on a tactical timescale. Here, we describe the heritage, design, and optical characterization of these targets and discuss their use during rover operations. The Mastcam-Z primary calibration target inherits features of camera calibration targets on the Mars Exploration Rovers, Phoenix and Mars Science Laboratory missions. This target will be regularly imaged during flight to accompany multispectral observations of the martian surface. The primary target consists of a gold-plated aluminum base, eight strong hollow-cylinder Sm
2
Co
17
alloy permanent magnets mounted in the base, eight ceramic color and grayscale patches mounted over the magnets, four concentric, ceramic grayscale rings and a central aluminum shadow post (gnomon) painted with an IR-black paint. The magnets are expected to keep the central area of each patch relatively free of Martian aeolian dust. The Mastcam-Z secondary calibration target is a simple angled aluminum shelf carrying seven vertically mounted ceramic color and grayscale chips and seven identical, but horizontally mounted ceramic chips. The secondary target is intended to augment and validate the calibration-related information derived from the primary target. The Mastcam-Z radiometric calibration targets are critically important to achieving Mastcam-Z science objectives for spectroscopy and photometric properties.
In the context of person-environment research in gerontology and psychology, urban planners and experts involved in die use of urban space should consider die potential of historical-artistic cities ...as healthy settings in which people may experience greater feelings of well-being.
Oregon State University, Corvallis, Oregon The prevalence of depression is high among the Spanish elderly; some studies have found a rate of depressive symptoms of 25%, although major depression is ...only present in l%of the population (Lobo et al., 1995, Imserso, 2006).
Hypothesis We hypothesized that posterior capsule thickness (PCT) would be greater on the dominant arm compared to the non-dominant arm. We also hypothesized that PCT would negatively correlate with ...glenohumeral internal rotation and scapular upward rotation. In addition, PCT would positively correlate with glenohumeral external rotation. However, currently PCT has not been measured nor have correlations been identified to exist with glenohumeral and scapular motion. Therefore, the purpose of the study was to determine if the posterior capsule was hypertrophied on the dominant arm and to identify if relationships exist with glenohumeral internal rotation (IR), external rotation (ER), and scapular upward rotation (SUR). Materials and methods PCT was measured using a 10-MHz transducer. Glenohumeral IR and ER was measured supine using a digital inclinometer. SUR was measure at 0°, 60°, 90°, and 120° of glenohumeral abduction using a modified digital inclinometer. Results PCT was greater on the dominant compared with the nondominant arm ( P = .001). A negative correlation was found between PCT and IR (–0.498, P = .0001). A positive correlation was found between PCT and ER (0.450, P = .002) and between PCT and SUR at 60°, 90°, and 120° of glenohumeral abduction (0.388, P = .006; 0.327, P = .023; 0.304, P = .036, respectively). Discussion This in vivo study demonstrated a hypertrophied posterior capsule and its association with GIRD, ER, and SUR. These observations suggest that PCT does occur on the throwing arm of baseball players and is linked with glenohumeral and scapular alterations. Conclusions This methodology could be used as a noninvasive screening evaluation for overhead athletes to identify those who may be at risk for shoulder injuries due to excessive capsular thickening.
Ankle sprains are common in athletes, with functional ankle instability (FAI) developing in approximately half of cases. The relationship between laxity and FAI has been inconclusive, suggesting that ...instability may be caused by insufficient sensorimotor function and dynamic restraint. Research has suggested that deafferentation of peripheral mechanoreceptors potentially causes FAI; however, direct evidence confirming peripheral sensory deficits has been elusive because previous investigators relied upon subjective proprioceptive tests.
To develop a method for simultaneously recording peripheral sensory traffic, joint forces, and laxity and to quantify differences between healthy ankles and those with reported instability.
Case-control study.
University laboratory.
A total of 29 participants (age = 20.9 ± 2.2 years, height = 173.1 ± 8.9 cm, mass = 74.5 ± 12.7 kg) stratified as having healthy (HA, n = 19) or unstable ankles (UA, n = 10).
Sensory traffic from muscle spindle afferents in the peroneal nerve was recorded with microneurography while anterior (AP) and inversion (IE) stress was applied to ligamentous structures using an ankle arthrometer under test and sham conditions.
Laxity (millimeters or degrees) and amplitude of sensory traffic (percentage) were determined at 0, 30, 60, 90, and 125 N of AP force and at 0, 1, 2, 3, and 4 Nm of IE torque. Two-factor repeated-measures analyses of variance were used to determine differences between groups and conditions.
No differences in laxity were observed between groups (P > .05). Afferent traffic increased with increased force and torque in test trials (P < .001). The UA group displayed decreased afferent activity at 30 N of AP force compared with the HA group (HA: 30.2% ± 9.9%, UA: 17.1% ± 16.1%, P < .05).
The amplitude of sensory traffic increased simultaneously with greater ankle motion and loading, providing evidence of the integrated role of capsuloligamentous and musculotendinous mechanoreceptors in maintaining joint sensation. Unstable ankles demonstrated diminished afferent traffic at low levels of force, suggesting the early detection of joint loading may be compromised.
To determine (1) the association between lifetime diagnosed concussion and lower extremity musculoskeletal injury (LE-MSI) among community rugby union players and (2) the sex specific risk of LE-MSI ...given concussion history among males and females.
Retrospective survey.
1037 (59.0% male, (612/1037), age: 31.6 ± 11.3 years) rugby players (10.1 ± 8.1 years played) completed an online survey to ascertain injury history. A chi-squared test of association was performed between concussion and LE-MSI; significant outcomes were followed-up with an odds ratio. A binary logistic regression with any LE-MSI (yes/no) as the outcome and concussion (yes/no) and sex (male/female) as predictors was performed to determine if there was a sex by concussion interaction.
There was an overall significant association between concussion and any LE-MSI(χ(1) = 13.055, p < 0.001, OR = 2.30 95%CI: 1.45, 3.65). Both male (OR = 2.21) and females (OR = 2.49) had significant associations for concussion and LE-MSI, but there were no differences between sex for risk of LE-MSI (R2 = 0.024, p = 0.999).
Community rugby players with a history of concussion are >2× more likely to also experience an LE-MSI than those without a history of concussion. There were no differences in the odds of LE-MSI between males and females with a history of diagnosed concussion. In line with current World Rugby injury prevention programs, future research should aim to reduce LE-MSI incidence to maximize player safety and wellness through targeted injury prevention and teams should utilize a conservative return to play protocols following concussion.
Peptidoglycan is an essential component of the bacterial cell envelope that contains glycan chains substituted by short peptide stems. Peptide stems are polymerized by D,D-transpeptidases, which make ...bonds between the amino acid in position four of a donor stem and the third residue of an acceptor stem (4-3 cross-links). Some bacterial peptidoglycans also contain 3-3 cross-links that are formed by another class of enzymes called L,D-transpeptidases which contain a YkuD catalytic domain. In this work, we investigate the formation of unusual bacterial 1-3 peptidoglycan cross-links. We describe a version of the PGFinder software that can identify 1-3 cross-links and report the high-resolution peptidoglycan structure of Gluconobacter oxydans (a model organism within the Acetobacteraceae family). We reveal that G. oxydans peptidoglycan contains peptide stems made of a single alanine as well as several dipeptide stems with unusual amino acids at their C-terminus. Using a bioinformatics approach, we identified a G. oxydans mutant from a transposon library with a drastic reduction in 1-3 cross-links. Through complementation experiments in G. oxydans and recombinant protein production in a heterologous host, we identify an L,D-transpeptidase enzyme with a domain distantly related to the YkuD domain responsible for these non-canonical reactions. This work revisits the enzymatic capabilities of L,D-transpeptidases, a versatile family of enzymes that play a key role in bacterial peptidoglycan remodelling.
PDF
