•Small particle sizes and slow crystallization exclude aggregates during freezing.•Ice exclusion processes not likely to form mm-scale spherical aggregates on Mars.•Particles become entrapped within ...the ice as aggregate size increases.•Sand and salts affected aggregation, but no mm-sized spherical aggregates formed.
The enigmatic and unexpected occurrence of coarse crystalline (gray) hematite spherules at Terra Meridiani on Mars in association with deposits of jarosite-rich sediments fueled a variety of hypotheses to explain their origin. In this study, we tested the hypothesis that freezing of aqueous hematite nanoparticle suspensions, possibly produced from low-temperature weathering of jarosite-bearing deposits, could produce coarse-grained hematite aggregate spherules. We synthesized four hematite nanoparticle suspensions with a range of sizes and morphologies and performed freezing experiments. All sizes of hematite nanoparticles rapidly aggregate during freezing. Regardless of the size or shape of the initial starting material, they rapidly collect into aggregates that are then too big to push in front of a stable advancing ice front, leading to incohesive masses of particles, rather than solid spherules. We also explored the effects of “seed” silicates, a matrix of sand grains, various concentrations of NaCl and CaCl2, and varying the freezing temperature on hematite nanoparticle aggregation. However, none of these factors resulted in mm-scale spherical aggregates. By comparing our measured freezing rates with empirical and theoretical values from the literature, we conclude that the spherules on Mars could not have been produced through the freezing of aqueous hematite nanoparticle suspensions; ice crystallization front instability disrupts the aggregation process and prevents the formation of mm-scale continuous aggregates.
Display omitted
We assessed the development of natural voiding function late in gestation and in the immediate postnatal period in a porcine model.
The study comprised 7 male fetal minipigs (median age 94 days, 0.88 ...gestation) and 7 male newborn pigs. In all pigs an ultrasonic probe was placed around the subcutaneous urethra and pressure catheters were placed in the bladder and rectum and in the amnionic cavity in the fetal pigs. The catheters were connected to pressure transducers as the flow probe was connected to a flow meter, and the recordings were sampled at a rate of 10 Hz on a personal computer.
The newborns had a median voiding frequency of 3.3 times per hour while the fetuses voided a median of 5.9 times per hour (p = 0.16). Both groups voided with a staccato flow at a frequency of 1 to 2 Hz, indicating voiding dyscoordination between the detrusor and urethra. Maximum flow rate increased from median 4.4 ml per minute (range 2.0 to 8.8) in the fetal group to median 10.9 (5.4 to 18.3) in the newborns (p = 0.07). While the minimum opening pressure remained unchanged (median 7.0 cm H
2O, range 5.7 to 13.0) vs median 7.6, (range 7.7 to 14.0, p = 0.57) the detrusor pressure at maximum flow decreased from median 22.4 cm H
2O (range 16.6 to 39.0) in the fetal pigs to 12.1 cm H
2O (8.3 to 22.3) in the newborns.
Fetal and newborn pigs have dyscordinated voiding with a staccato flow. While the urethral opening pressure appears to be unchanged, the detrusor pressure at maximum flow decreases during the last period of gestation, indicating decreased urethral resistance. These findings are in accordance with observations made in human infants.
Objectives: To present data on the comparative and interactive workplace costs of depression relative to other health problems in the workforce of a large employer. Methods: The World Health ...Organization Health and Work Performance Questionnaire was used to assess self-reported health problems and work performance. Survey data were linked to medical-pharmacy claims data. Regression analysis was used to assess comparative effects of depression in the absence and presence of comorbidities on Health and Work Performance Questionnaire measures of work performance. Results: Depression had the largest individuallevel effect on work performance of any condition examined. Several comorbid conditions exacerbated the effect of depression, but had no effects in the absence of depression. Conclusions: Depression is a strong predictor of decrements in work performance. Other conditions that often co-occur with depression, including anxiety and fatigue-sleep disturbance, exacerbate the adverse effect of depression.
Routine use of ultrasound during pregnancy has emphasized the need for greater knowledge about normal and abnormal voiding function during fetal live. We describe the developmental changes in lower ...urinary tract function from the middle of the second to the early third trimester of gestation.
The study included 22 male fetal pigs of 13 pregnant Goettingen minipigs (gestational period 111 to 115 days) with 11 fetuses in the middle of the second (median 61.5 days, 0.55 of term) and 11 fetuses in the beginning of the third trimester of gestation (median 80 days, 0.72 of term). With the sow under isoflurane anesthesia catheters were placed in the bladder, rectum and amniotic cavity of the fetuses, and a flow probe was placed around the distal urethra. After the sow was at light sleep urethral flow, amniotic pressure, abdominal pressure and bladder pressure were recorded a median of 241 minutes.
The recordings of 14 fetuses were evaluable. In the middle of the second trimester the fetuses showed an almost constant dribbling with a median flow of 0.2 ml. per minute and a median of 4 concomitant bladder contractions per minute of median 3.5 cm. H
2O (detrusor pressure). At the beginning of the third trimester the fetuses had periods of staccato flow (median 0.2 ml. per minute, staccato frequency 1 to 2 Hz.) on top of contractions (median 4 contractions per minute, median detrusor pressure 5.5 cm. H
2O) with no flow between voidings.
Development of storage and voiding function in male pigs occurs between the mid-second and early third trimester of gestation, together with emergence of striated sphincter bursting activity, which interrupts flow in the urethra during the voiding phase.
Some evidence suggests that medications that modulate both serotonin and norepinephrine may be more effective than selective serotonin-reuptake inhibitors (SSRIs) in severe major depressive disorder ...(MDD). This prospective pragmatic trial tests this hypothesis. Patients with severe MDD were randomly assigned to either duloxetine (a serotonin and norepinephrine-reuptake inhibitor) or physicians' choice of four generic SSRIs. Nonblinded, flexibly dosed treatment was used to mimic clinical practice. To address potential investigator bias, the patient-reported Quick Inventory of Depressive Symptomatology Self-Report (QIDS-SR) was used as the primary efficacy outcome measure. A total of 750 outpatients (19.2%, African descent; 14.8%, Hispanic) were randomized. The primary outcome, remission at week 12 by QIDS-SR, was numerically greater for duloxetine compared with SSRIs (36 vs. 32%), but this difference was not statistically significant. Mean changes in secondary outcomes were significantly superior in favor of duloxetine for the Hamilton Depression Scale-17 item, the Brief Pain Inventory, and the Sheehan Disability Scale. Remission superiority on the QIDS-SR was not achieved. Significantly greater benefit for duloxetine compared with SSRIs was demonstrated on measures of pain and functioning. Study demographics suggest a more generalizable racial and ethnic population than is typical in randomized clinical trials.
The porcine urological system is similar anatomically and physiologically to that of humans. Swine have a true multirenculate, multipapillate kidney with a calyceal system like that of humans. The ...gross anatomic and histologic characteristics of the porcine and the human kidney are more similar than most other commonly used laboratory animals. The physiologic functions of the urinary system including urodynamic parameters are also similar to humans. Swine have been used extensively as models of urologic conditions in humans, most commonly in obstructive urologic syndromes. A large number of investigative procedures can be performed in one experiment both in acute and chronic models. Recently, a new technique of surgically induced antenatal lower urinary tract obstruction in swine has been developed.
The Mars Sample Return Planning Group 2 (MSPG2) was tasked with identifying the steps that encompass all the curation activities that would happen within the MSR Sample Receiving Facility (SRF) and ...any anticipated curation-related requirements. An area of specific interest is the necessary analytical instrumentation. The SRF would be a Biosafety Level-4 facility where the returned MSR flight hardware would be opened, the sample tubes accessed, and the martian sample material extracted from the tubes. Characterization of the essential attributes of each sample would be required to provide enough information to prepare a sample catalog used in guiding the preparation of sample-related proposals by the world's research community and informing decisions by the sample allocation committee. The sample catalog would be populated with data and information generated during all phases of activity, including data derived concurrent with Mars 2020 sample-collecting rover activity, sample transport to Earth, and initial sample characterization within the SRF. We conclude that initial sample characterization can best be planned as a set of three sequential phases, which we have called Pre-Basic Characterization (Pre-BC), Basic Characterization (BC), and Preliminary Examination (PE), each of which requires a certain amount of instrumentation. Data on specific samples and subsamples obtained during sample safety assessments and time-sensitive scientific investigations would also be added to the catalog. There are several areas where future work would be beneficial to prepare for the receipt of samples, which would include the design of a sample tube isolation chamber and a strategy for opening the sample tubes and removing dust from the tube exteriors. Executive Summary All material collected from Mars (gases, dust, rock, regolith) would need to be carefully handled, stored, and analyzed following Earth return to minimize the alteration or contamination that could occur on Earth and maximize the scientific information that can be attained from the samples now and into the future. A Sample Receiving Facility (SRF) is where the Earth Entry System (EES) would be opened and the sample tubes opened and processed after they land on Earth. Samples should be accessible for research in biocontainment for time-sensitive studies and eventually, when deemed safe for release after sterilization or biohazard assessment, should be transferred out of biocontainment for allocation to scientific investigators in outside laboratories. There are two main mechanisms for allocation of samples outside the SRF: 1) Wait until the implementation of the Sample Safety Assessment Protocol (Planetary Protection) results concludes that the samples are non-hazardous, 2) Render splits of the samples non-hazardous by means of sterilization. To make these samples accessible, a series of observations and analytical measurements need to be completed to produce a sample catalog for the scientific community. Specialist members of the Mars Sample Return Planning Group Phase 2 (MSPG2), referred to here as the Curation Focus Group, have identified four curation goals that encompass all of the activities within the SRF: 1.Documentation of the state of the sample tubes and their contents prior to opening, 2.Inventory and tracking of the mass of each sample, 3.Preliminary assessment of lithology and any macroscopic forms of heterogeneity (on all the samples, non-invasive, in pristine isolators), 4.Sufficient characterization of the essential attributes of each sample to prepare a sample catalog and respond to requests by the sample allocation committee (partial samples, invasive, outside of pristine isolators). The sample catalog will provide data for the scientific community to make informed requests for samples for scientific investigations and for the approval of allocations of appropriate samples to satisfy these requests. The sample catalog would be populated with data and information generated during all phases of activity, including data derived from the landed Mars 2020 mission, during sample collection and transport to Earth, and reception within the Sample Receiving Facility. Data on specific samples and subsamples would also be generated during curation activities carried out within the Sample Receiving Facility and during sample safety assessments, time-sensitive studies, and a series of initial sample characterization steps we refer to as Pre-Basic Characterization (Pre-BC), Basic Characterization (BC), and Preliminary Examination (PE) phases. A significant portion of the Curation Focus Group's efforts was to determine which instrumentation would be required to produce a sample catalog for the scientific community and how and when certain instrumentation should be used. The goal is to provide enough information for the PIs to request material for their studies but to avoid facilitating studies that target scientific research that is better left to peer-reviewed competitive processes. We reviewed the proposed scientific objectives of the International MSR Objectives and Samples Team (iMOST) (Beaty
2019) to make sure that the instrumentation suggested is sufficient to cover these key science planning questions (Table 1; Section S-6). It was determined that for Pre-Basic Characterization, two instruments are required, a Magnetometer (see Section S-1.1) and an X-ray Computed Tomography scanner (XCT see Section S-1.2). For Basic Characterization, there are four instruments that are considered necessary, which are analytical balance(s) (see Section S-2.1), binocular microscopes (see Section S-2.2), and multispectral imaging and hyperspectral scanning systems (see Section S-2.3). Then in Preliminary Examination, there is a set of instruments that should be available for generating more detailed information for the sample catalog. These are a Variable Pressure-Field Emission Scanning Electron Microscope (VP-FE-SEM see Section S-3.1), Confocal Raman spectrometer (see Section S-3.2), Deep UV Fluorescence (see Section S-3.3), a Fourier Transform Infrared Spectrometer (see Section S-3.4), a Micro X-ray Diffractometer (see Section S-3.5), X-ray Fluorescence Spectrometer (see Section S-3.6), and Petrographic and Stereo Microscope (see Section S-3.7). All instruments are summarized in Table 1. Finally, our Curation Focus Group has outlined several specific findings for sample curation within the SRF to complete the sample catalog prior to sample distribution and made several recommendations for future work (summarized in Section 8.1) to build upon the efforts that generated this report. List of Findings
Immediately after Earth landing, the spacecraft would be recovered and placed in a container designed to control and stabilize its physical conditions. The optimum temperature (T
) of the sample tubes during transport to the Sample Receiving Facility (SRF) should be the same as the operating temperature of the SRF to avoid unnecessary temperature shock.
The Sample Receiving Facility (SRF) should operate at room temperature (∼15-25°C), and the samples should be held at this temperature through all steps of initial sample characterization, with the option for cold storage of subsamples available in the SRF when needed.
To minimize the interaction of Earth atmospheric gases and gases that are in the sealed sample tubes, once the dust is removed from the exterior of the sample tubes, they should be placed into individual sample tube isolation chambers (STIC) as quickly as possible.
There are compelling reasons to perform penetrative 3D imaging prior to opening the sample tubes. A laboratory-based X-ray Computed Tomography scanner is the best technique to use and the least damaging to organics of the penetrative imaging options considered.
To avoid cross contamination between samples, it is recommended that, for processing through the isolators, the samples are organized into groups that have like properties. Given what we know about the geology of Jezero Crater, a reasonable starting assumption is five such groups.
The output of the initial sample characterization, and a key function of the curation activities within the Sample Receiving Facility, is to produce a sample catalog that would provide relevant information on the samples' physical and mineralogical/chemical characteristics (derived from the Pre-Basic Characterization, Basic Characterization, and Preliminary Examination investigations), sample safety assessments, time-sensitive studies, and information derived from mission operations to enable allocation of the most appropriate materials to the scientific community.
A staffing model for curation activities, including technical support and informatics/ documentation support, should be developed (as part of ongoing Sample Receiving Facility development) to ensure that the Sample Receiving Facility is staffed appropriately to support sample curation activities.
To reduce the risk of catastrophic loss of samples curated in a single facility up to, and including, decadal timescales, the sample collection should be split-once it is possible to do so-and housed in more than one location for the purpose of maximizing the long-term safety of the collection.
The objective of the present study was to evaluate how feed withdrawal and transportation influenced the cecal environment and cecal populations of Campylobacter in swine. Four miniature Yucatan ...gilts (8.8 kg), naturally infected with Campylobacter jejuni, were surgically implanted with cecal cannulas. The gilts were fasted for 48 h. Samples of cecal contents were collected for 7 days prior to and for 7 days after the fast, and mean values were determined for pH, volatile fatty acids (VFA), and CFU enumeration of C. jejuni. This was replicated three times. In another trial, gilts (full-fed) were transported in a livestock trailer for 4 h and cecal samples were collected before and after transport and analyzed for pH, VFA, and CFU. Following a 48-h fast, cecal pH increased (P < 0.05) by 1 unit; acetic and propionic acids decreased (P < 0.05) by 61% and 71%, respectively; and there was a twofold log10 increase (P < 0.05) in CFU/g cecal content of C. jejuni. Values of pH, VFA, and CFU of C. jejuni did not change in cecal samples from gilts following transportation. These data are important for food safety considerations because feed withdrawal, commonly associated with shipping and slaughter, can increase Campylobacter concentrations in the pig intestinal tract.
Current experimental vitreous substitutes only replace the physical functions of the natural vitreous humor. Removal of the native vitreous disrupts oxygen homeostasis in the eye, causing oxidative ...damage to the lens that likely results in cataract formation. Neither current clinical treatments nor other experimental vitreous substitutes consider the problem of oxidative stress after vitrectomy. To address this problem, biomimetic hydrogels are prepared by free radical polymerization of poly(ethylene glycol) methacrylate and poly(ethylene glycol) diacrylate. These hydrogels have similar mechanical and optical properties to the vitreous. The hydrogels are injectable through small‐gauge needles and demonstrate in vitro biocompatibility with human retinal and lens epithelial cells. The hydrogels and added vitamin C, an antioxidant, show a synergistic effect in protecting ocular cells against reactive oxygen species, which fulfills a chemical function of the natural vitreous. These hydrogels have the potential to prevent post‐vitrectomy cataract formation and reduce the cost of additional surgeries.
Poly(ethylene glycol)‐based hydrogels are proposed as vitreous substitutes. The hydrogels have similar physical and optical properties as the natural vitreous humor. With the addition of vitamin C, the hydrogels protect the lens cells from reactive oxygen species. This is the first report on a vitreous substitute that can replace both the physical and chemical roles of the natural vitreous.
PDF
