Mars atmosphere. The imprint of atmospheric evolution in the D/H of Hesperian clay minerals on Mars.

The deuterium-to-hydrogen (D/H) ratio in strongly bound water or hydroxyl groups in ancient martian clays retains the imprint of the water of formation of these minerals. Curiosity's Sample Analysis at Mars (SAM) experiment measured thermally evolved water and hydrogen gas released between 550° and 950°C from samples of Hesperian-era Gale crater smectite to determine this isotope ratio. The D/H value is 3.0 (±0.2) times the ratio in standard mean ocean water. The D/H ratio in this ~3-billion-year-old mudstone, which is half that of the present martian atmosphere but substantially higher than that expected in very early Mars, indicates an extended history of hydrogen escape and desiccation of the planet.

Evaluation of UT/LS hygrometer accuracy by intercomparison during the NASA MACPEX mission.

Acquiring accurate measurements of water vapor at the low mixing ratios (< 10 ppm) encountered in the upper troposphere and lower stratosphere (UT/LS) has proven to be a significant analytical challenge evidenced by persistent disagreements between high-precision hygrometers. These disagreements have caused uncertainties in the description of the physical processes controlling dehydration of air in the tropical tropopause layer and entry of water into the stratosphere and have hindered validation of satellite water vapor retrievals. A 2011 airborne intercomparison of a large group of in situ hygrometers onboard the NASA WB-57F high-altitude research aircraft and balloons has provided an excellent opportunity to evaluate progress in the scientific community toward improved measurement agreement. In this work we intercompare the measurements from the Midlatitude Airborne Cirrus Properties Experiment (MACPEX) and discuss the quality of agreement. Differences between values reported by the instruments were reduced in comparison to some prior campaigns but were nonnegligible and on the order of 20% (0.8 ppm). Our analysis suggests that unrecognized errors in the quantification of instrumental background for some or all of the hygrometers are a likely cause. Until these errors are understood, differences at this level will continue to somewhat limit our understanding of cirrus microphysical processes and dehydration in the tropical tropopause layer.

Lack of menstrual cycle effects on hypothalamic-pituitary-adrenal axis response to insulin-induced hypoglycaemia.

OBJECTIVE: Limited data are available on the effects of the menstrual cycle on the hypothalamic-pituitary-adrenal axis (HPA) function. This study evaluates HPA axis reactivity to insulin-induced hypoglycaemia over the menstrual cycle. PATIENTS: Twelve normal women were randomized to placebo and evaluated during three successive menstrual cycles. Menstrual phase was documented by menstrual diary and by oestradiol and progesterone levels at the time of each insulin tolerance test (ITT). Six normal men were included as a comparison in the statistical analysis. MEASUREMENTS: Afternoon ITTs were performed initially on the second or third day of menses in women, then seven more ITTs followed at one or two week intervals during the next 10 weeks. Serum measurements of glucose, adrenocorticotrophin (ACTH) and cortisol were obtained. RESULTS: The glucose and ACTH responses to the ITTs were similar between men and women. Cortisol levels at baseline and during the test were higher in men than in women, although the amount of change was similar. Glucose, ACTH and cortisol response to insulin-induced hypoglycaemia did not vary over the menstrual cycle or during repeat testing in men or women. CONCLUSIONS: These data show that it is unnecessary to control for menstrual cycle during insulin tolerance tests performed at 1600 hours. It is, however, necessary to control for the effect of sex on cortisol levels. Repeat testing more than one week apart does not appear to influence the glucose, ACTH or cortisol response to insulin stress.

Results of late surgery for presumed congenital cataracts.

We reviewed the results of cataract extraction and visual rehabilitation in 76 eyes of 47 infants and children with presumed congenital cataracts who were first seen after they were 10 months old. Eighteen patients underwent surgery for unilateral cataracts, including five patients with persistent hyperplastic vitreous, five with posterior lenticonus, one with a nuclear cataract, six with posterior subcapsular cataracts, and one with a lamellar cataract. Of these 18 patients, seven (39%) attained a visual acuity of 20/60 or better, one (6%) had a visual acuity of 20/100, and ten (60%) had a visual acuity of 20/200 or worse. Twenty-nine patients (62 eyes) underwent bilateral cataract extraction. The visual acuity could be measured in 22 patients (44 eyes). Visual acuity improved to 20/60 or better in 32 eyes (73%), was between 20/70 and 20/150 in 11 eyes (25%), and became worse than 20/200 in one eye (2%). Results were good in patients with persistent hyperplastic primary vitreous, posterior lenticonus, and bilateral cataracts.

Adjustable suture strabismus surgery.

We examined 333 patients between the ages of 11 and 70 years who underwent strabismus surgery with adjustable sutures over a ten-year period. The type of strabismus, the number and amount of adjustments, the postoperative drift, and complications were evaluated. A large percentage of patients required adjustment to obtain the desired postoperative position. The postoperative drift patterns were characteristic for each type of preoperative deviation and were similar to that reported for nonadjustable procedures. Adjustable suture techniques were especially helpful in selected horizontal deviations, vertical deviations, and the more complex strabismus problems. The complications from adjustable suture operations in this series were minimal.

The effects of ear removal on senescence and metabolism of maize.

Ears were removed from field grown maize (Zea mays L.) to determine the effects on senescence and metabolism and to clarify conflicting literature reports pertaining to these effects. Ears were removed at three days after anthesis and comparisons were made of changes in metabolism between eared and earless plants until grain of the eared plants matured as judged by black layer formation.The initial visual symptom following ear removal was the development of reddish colored leaves. As judged by leaf yellowing, the removal of ears not only initiated an earlier onset but enhanced the rate of senescence. With this exception, the visual patterns of senescence were similar for earless and eared plants. Other characteristics associated with ear removal were: (a) marked decrease in dry weight and reduced N accumulation by the whole plant; (b) progressive, parallel decreases in leaf reduced N, nitrate reductase activity, and chlorophyll; (c) increases in carbohydrate content of both the leaf and stalk and of reduced N in the stalk. These changes indicate that ear removal reduced photosynthesis and nitrate reduction by approximately equal proportions and that the stalk serves as an alternate sink for both carbohydrate and nitrogen.The remobilization of nitrogen from the leaf was not dependent on the presence of an ear. A logical reason for the more rapid loss of nitrogen from the leaf of the earless plants appears to be the cessation of nitrate uptake and/or flux of nitrate to the leaves.From these results and from related experiments we tentatively conclude that the loss of nitrogen from the leaf is a major cause of death of the intact maize plant.

Availability of reduced N and carbohydrates for ear development of maize.

Changes in dry weights, reduced N, nitrate, and nitrate reductase activity of various plant parts of the above ground vegetation (stover) and ears of field grown maize were measured at intervals between anthesis and grain maturity. Nonstructural carbohydrate contents were also measured in some instances. Changes in dry weight and reduced N content were used to approximate net in situ photosynthetic and nitrate assimilation activities and to determine whether the availability of photosynthate or reduced N was limiting grain production.Of the five hybrids studied, all showed extensive remobilization (loss) of reduced N from the stover during grain development. This loss of stover N was initiated by 18 to 21 days after anthesis. Most of this loss of N (about 70%) was from the leaves. In contrast, three of the five hybrids had more vegetative dry weight at grain maturity than at anthesis, while the loss of stover dry weight by the other two hybrids was negligible. By 42 days after anthesis when the bulk of the ear weight had been acquired, the average gain in stover dry weight for the five hybrids was 12% while the loss of stover reduced N was 28%. Where measured, the increase in stover dry weight was largely due to deposition of carbohydrates in the stalk. These results show that the photosynthetic capacity was adequate while nitrate reduction capacity was inadequate for ear demands. The changes in the rate of accumulation of dry weight and reduced N by the ear indicated that the rate of supply of reduced N to the ear could have limited ear development for one of the five hybrids. The dry weight and carbohydrate (where measured) accumulation in the vegetation during the first 42 days after anthesis infers that the rate of supply of photosynthate to the ear was probably not a limiting factor for any of the five hybrids.The maximum remobilization of stover N during grain development was 1.8 g N plant(-1) for the genotypes examined, while the amount of reduced N accumulated by the grain varied from 1 to 5 g plant(-1). The amount of newly reduced N (nitrate reduced after anthesis) provided from 48 to 72% of the total N accumulated by the ear. The relative amounts of newly reduced N and remobilized N vary with genotype and environment. With respect to insuring high productivity, it was concluded that there is more flexibility in the system (genotype and environment) for increasing the supply of newly reduced N than in enhancing the remobilization of vegetative N.