936 research outputs found
The First Three Rungs of the Cosmological Distance Ladder
It is straightforward to determine the size of the Earth and the distance to
the Moon without making use of a telescope. The methods have been known since
the 3rd century BC. However, few amateur or professional astronomers have
worked this out from data they themselves have taken. Here we use a gnomon to
determine the latitude and longitude of South Bend, Indiana, and College
Station, Texas, and determine a value of the radius of the Earth of 6290 km,
only 1.4 percent smaller than the true value. We use the method of Aristarchus
and the size of the Earth's shadow during the lunar eclipse of 2011 June 15 to
derive an estimate of the distance to the Moon (62.3 R_Earth), some 3.3 percent
greater than the true mean value. We use measurements of the angular motion of
the Moon against the background stars over the course of two nights, using a
simple cross staff device, to estimate the Moon's distance at perigee and
apogee. Finally, we use simultaneous CCD observations of asteroid 1996 HW1
obtained with small telescopes in Socorro, New Mexico, and Ojai, California, to
derive a value of the Astronomical Unit of (1.59 +/- 0.19) X 10^8 km, about 6
percent too large. The data and methods presented here can easily become part
of a beginning astronomy lab class.Comment: 34 pages, 11 figures, accepted for publication in American Journal of
Physic
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Methods and systems for performing submucosal medical procedures
Instruments, systems and methods are provided for performing submucosal medical procedures in a desired area of the digestive tract using endoscopy. Instruments include a safe access needle injection instrument, a submucosal tunneling instrument, a submucosal dissection instrument, a mucosal resection device. Systems include a combination of one or more of such instruments with or without injectable agents. Embodiments of various methods for performing the procedures are also provided.Board of Regents, University of Texas Syste
Molecular cloning of the rat proteinase-activated receptor 4 (PAR4)
BACKGROUND: The proteinase-activated receptor 4 (PAR4) is a G-protein-coupled receptor activated by proteases such as thrombin and trypsin. Although activation of PAR4 has been shown to modulate rat gastrointestinal motility, the rat PAR4 sequence was unknown until now. This study aimed to identify the rat PAR4 cDNA. RESULTS: The cDNA coding for the rat PAR4 homologue was cloned from the duodenum. Northern blots demonstrated a 3.0 kb transcript in the duodenum. Protein homology with mouse and human counterparts was 90% and 75% respectively. PAR4 is expressed predominantly in the esophagus, stomach, duodenum and the spleen. When expressed in COS cells, PAR4 is activated by trypsin (1 nM), thrombin (50 nM), mouse PAR4 specific peptide (500 Ī¼M) and a putative rat PAR4 specific activating peptide (100 Ī¼M), as measured by intracellular Ca(2+)-changes. CONCLUSIONS: We have identified and characterized cDNA encoding the rat PAR4 homologue. PAR4 is expressed predominantly in the upper gastrointestinal tract. It is activated by trypsin, thrombin and its newly identified rat PAR4 specific activating peptide
Evolution of mud-crack patterns during repeated drying cycles
In mud, crack patterns are frequently seen with either an approximately rectilinear or hexagonal tiling. Here we show, experimentally, how a desiccation crack pattern changes from being dominated by 90Ā° joint angles, to 120Ā° joint angles. Layers of bentonite clay, a few mm thick, were repeatedly wetted and dried. When dried, the layers crack. These cracks visibly close when rewetted, but a similar crack pattern forms when the layer is redried, with cracks forming along the lines of previously open cracks. Time-lapse photography was used to show how the sequence in which individual cracks open is different in each generation of drying. The geometry of the crack pattern was observed after each of 25 generations of wetting and drying. The angles between cracks were found to approach 120Ā°, with a relaxation time of approximately 4 generations. This was accompanied by a gradual change in the position of the crack vertices, as the crack pattern evolved. A simple model of crack behavior in a layer where the positions of previously open cracks define lines of weakness is developed to explain these observations
Factors related to abdominal pain in gastroparesis: contrast to patients with predominant nausea and vomiting
Background Factors associated with abdominal pain in gastroparesis are incompletely evaluated and comparisons of pain vs other symptoms are limited. This study related pain to clinical factors in gastroparesis and contrasted pain/discomfortā with nausea/vomitingāpredominant disease. Methods Clinical and scintigraphy data were compared in 393 patients from seven centers of the NIDDK Gastroparesis Clinical Research Consortium with moderateāsevere (Patient Assessment of Upper Gastrointestinal Disorders Symptoms [ PAGI ā SYM ] scoreĀ ā„3) vs noneāmild ( PAGI ā SYM Ā <Ā 3) upper abdominal pain and predominant pain/discomfort vs nausea/vomiting. Key Results Upper abdominal pain was moderateāsevere in 261 (66%). Pain/discomfort was predominant in 81 (21%); nausea/vomiting was predominant in 172 (44%). Moderateāsevere pain was more prevalent with idiopathic gastroparesis and with lack of infectious prodrome (PĀ ā¤Ā 0.05) and correlated with scores for nausea/vomiting, bloating, lower abdominal pain/discomfort, bowel disturbances, and opiate and antiemetic use (PĀ <Ā 0.05), but not gastric emptying or diabetic neuropathy or control. Gastroparesis severity, quality of life, and depression and anxiety were worse with moderateāsevere pain (PĀ ā¤Ā 0.008). Factors associated with moderateāsevere pain were similar in diabetic and idiopathic gastroparesis. Compared to predominant nausea/vomiting, predominant pain/discomfort was associated with impaired quality of life, greater opiate, and less antiemetic use (PĀ <Ā 0.01), but similar severity and gastric retention. Conclusions & Inferences Moderateāsevere abdominal pain is prevalent in gastroparesis, impairs quality of life, and is associated with idiopathic etiology, lack of infectious prodrome, and opiate use. Pain is predominant in one fifth of gastroparetics. Predominant pain has at least as great an impact on disease severity and quality of life as predominant nausea/vomiting.Peer Reviewedhttp://deepblue.lib.umich.edu/bitstream/2027.42/97520/1/nmo12091.pd
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