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At least 235 records · Page 13Linked to original sources

PubMed2005

511 keV photons from superconducting cosmic strings.

We show that a tangle of light superconducting strings in the Milky Way could be the source of the observed 511 keV emission from electron-positron annihilation in the Galactic bulge. The scenario predicts a flux that is in agreement with observations if the strings are at the approximately 1 TeV scale, making the particle physics within reach of planned accelerator experiments. The emission is directly proportional to the galactic magnetic field, and future observations should be able to differentiate the superconducting string scenario from other proposals.

Journal Article↗

PubMed2006

Producing a scale-invariant spectrum of perturbations in a Hagedorn phase of string cosmology.

We study the generation of cosmological perturbations during the Hagedorn phase of string gas cosmology. Using tools of string thermodynamics we provide indications that it may be possible to obtain a nearly scale-invariant spectrum of cosmological fluctuations on scales which are of cosmological interest today. In our cosmological scenario, the early Hagedorn phase of string gas cosmology goes over smoothly into the radiation-dominated phase of standard cosmology, without having a period of cosmological inflation.

Journal Article↗

PubMed2004

Correlation filter: an accurate approach to detect and locate low contrast character strings in complex table environment.

Correlation has been used extensively in object detection field. In this paper, two kinds of correlation filters, Minimum Average Correlation Energy (MACE) and Extended Maximum Average Correlation Height (EMACH), are applied as adaptive shift locators to detect and locate smudgy character strings in complex tabular color flight coupon images. These strings in irregular tabular coupon are computer-printed characters but of low contrast and could be shifted out of the table so that we cannot detect and locate them using traditional algorithms. In our experiment, strings are extracted in the preprocessing phase by removing background and then based on geometric information, two correlation filters are applied to locate expected fields. We compare results from two correlation filters and demonstrate that this algorithm is a high accurate approach.

Journal Article↗

PubMed1979

Purse string placement for staple anastomosis using the end-to-end anastomosis stapling instrument.

There may be technical difficulties in the use of recommended clamp for the insertion of the purse-string suture during the construction of an end-to-end staple anastomosis. Hand sewing the purse string eliminates some of the problems, but unless the suture is positioned within a few millimetres of the cut edge of the bowel, ischaemic tissue may be included in the staple line. In dogs, this leads to anastomotic dehiscence. The anastomosis may, however, be protected by excising the ischaemic tissue and reinforcing the staple line with sutures. An "over and over" purse-string technique is now preferred to minimize the risk of this occurring.

Animals↗

PubMed2001

PCR detection of Helicobacter pylori in string-absorbed gastric juice.

Molecular methods for detection of Helicobacter pylori infection have been shown to be highly sensitive in gastric biopsies and cultures. The objective of this work was to compare PCR detection of H. pylori DNA in string-absorbed gastric juice and in gastric biopsies. The study was performed in 47 dyspeptic adult patients undergoing endoscopy, and infection was detected by amplification of a segment of H. pylori ureA gene. Of the 29 patients positive in biopsy analysis, 23 (79%) were also positive in the gastric string. PCR analysis of gastric strings is a sensitive and safe procedure to detect H. pylori when endoscopy is not indicated, and may be of great clinical and epidemiological usefulness in determining effectiveness of eradication therapies, typing virulence genes and detecting antibiotic resistance mutations.

Adult↗

PubMed1985

Strings containing left bundle branch conductive tissue in the left ventricle. Observations in man.

Several reports have demonstrated the presence of strings within the heart chambers e.g.: on the basis of autopsy materials (Goforth 1926, Knoblich et al. 1962, Hudson 1965, Gould 1968, Roberts 1969, Franck 1970, Olsen & Valentine 1972) or by echocardiography (Nishimura et al. 1981, Choo et al. 1982, Lindvall et al. 1982, Asmussen submitted for publication). Prompted by the echocardiographic observations by Asmussen (Asmussen submitted for publication) we tested the hypothesis that left ventricular strings may contain left bundle branch conductive tissue. During a six months' survey period at the Laboratory of Pediatric Pathology we found two such cases. It is suggested that left bundle branch block and/or hemiblock may be a consequence of this abnormality in the event of stretching or rupture of such strings.

Bundle-Branch Block↗

PubMed2002

Reflection of drill-string extensional waves at the bit-rock contact.

Downward propagating extensional waves are partially reflected at the bit-rock contact. The evaluation of the reflection coefficient is important to obtain while drilling information about the acoustic properties of the formations. The scope of this work is to estimate the bit-rock reflection coefficient, assuming a flat drill bit in perfect contact with the formation. Using the low-frequency approximation, which holds when the wavelength is much larger than the lateral dimensions of the borehole, the drill-string is assumed to be a laterally free rod, and the formation an homogeneous and isotropic medium. This work shows that the reflection coefficient of the extensional waves depends, along with the elastic properties of the formation, on the ratio of the cross sections of the drill-string and borehole. The impedance of the drilled rock can be calculated from the measured reflection coefficient, which is related to the amplitude of waves produced in the string and in the formation by a working drill-bit.

Journal Article↗

PubMed2000

Reconstruction of bowing point friction force in a bowed string

A method is presented for reconstructing the friction force and the velocity at the bowing point of a string excited by a rosined bow sliding transverse to the string. Two versions of the method of reconstruction are presented, each approximate in different ways, but both capable of sufficient accuracy to allow useful application to problems of understanding frictional interactions in this dynamical system. The method is illustrated with simulated data to verify its accuracy, and results are shown for two contrasting cases of observed stick-slip string motion. As has been found in other investigations, the friction force during sliding is not determined by the instantaneous sliding speed. The results seem to be compatible with a thermally based model of rosin friction.

Journal Article↗

PubMed1992

DNA sequencing by primer walking with strings of contiguous hexamers.

When template DNA is saturated with a single-stranded DNA binding protein (SSB), strings of three or four contiguous hexanucleotides (hexamers) can cooperate through base-stacking interactions to prime DNA synthesis specifically from the 3' end of the string. Under the same conditions, priming by individual hexamers is suppressed. Strings of three of four hexamers representing more than 200 of the 4096 possible hexamers primed easily readable sequence ladders at more than 75 different sites in single-stranded or denatured double-stranded templates 6.4 kilobases to 40 kilobase pairs long, with a success rate of 60 to 90 percent. A synthesis of 1 micromole of hexamer supplies enough material for thousands of primings, so multiple libraries of all 4096 hexamers could be distributed at a reasonable cost. Such libraries would allow rapid and economical sequencing. Automating this strategy could increase the speed and efficiency of large-scale DNA sequencing by at least an order of magnitude.

Base Sequence↗

PubMed2001

Validation of the string test for the recovery of Helicobacter pylori from gastric secretions and correlation of its results with urea breath test results, serology, and gastric pH levels.

The efficacy of the string culture test to isolate Helicobacter pylori from gastric secretions of 28 volunteers was studied. With the urea breath test (UBT) as the "gold standard," the string culture test showed a sensitivity of 75% and a specificity of 100%. The results of string culture did not correlate with the UBT results, with serum antibody levels, or with the pH levels of gastric secretions.

Adult↗

PubMed1997

CT analysis of bowed stringed instruments.

PURPOSE: To determine the utility of computed tomography (CT) for the noninvasive evaluation of bowed stringed instruments. MATERIALS AND METHODS: Thirty-seven instruments that ranged in quality from student instruments to exquisite Stradivarius violins were analyzed with CT. Accuracy of thickness measurements was determined from 24 measurements of cross-sectional pieces sawed from a student violin. Accuracy of density measurements was determined from 328 CT attenuation measurements of 16 woods used in stringed instruments. RESULTS: Substantial differences of normal structure were noted between the masterpieces crafted in Cremona, Italy, and factory-produced student instruments. Unexpected defects were detected in nine of 14 instruments older than 100 years and ranged from a few wormholes (eight instruments) to many wormholes and extensive repair (one violin). CT thickness and attenuation measurements correlated well to the line of identity with actual measurements (P < .0001). Two cellos and a viola have been constructed from CT-derived information. The viola was awarded a gold medal at a recent international competition. CONCLUSION: CT provides the modern luthier and acoustic scientist with a unique tool for characterization of normal structure, defects, and repair and for accurate measurements of wood thickness and density. CT-derived information aids in the replication of original masterpieces. CT evaluation may have an important role in the valuation, insurance, and identification of valuable stringed instruments.

Equipment Design↗

PubMed1984

A comment on equating information with symbol strings.

Symbol strings are advanced as the informational basis for many biological, physiological, and psychological phenomena. The role ascribed to them is that of indicating or directing states of affairs. Pattee has suggested that nature exploits information in this quasi-linguistic sense sparingly, that symbol strings are limited in detail, and that their relation to dynamics is one of complementation. A different, nonsymbolic view of information that addresses how animals can guide their locomotion in cluttered surroundings has been pursued by Gibson. It has considerable generality: information is low-dimensional qualitative properties of low-energy fields, lawfully generated by properties of systems and surround. It is argued that in the absence of information in Gibson's specificational sense, information in the indicational-injunctional sense is ineffective, and it is suggested that perplexities about the selective content of symbol strings may be resolved by a thoroughgoing understanding of Gibsonian information.

Animals↗

PubMed1998

Self-evolution in a constructive binary string system.

We examine the qualitative dynamics of a catalytic self-organizing system of binary strings that is inspired by the chemical information processing metaphor. A string is interpreted in two different ways: either (a) as raw data or (b) as a machine that is able to process another string as data in order to produce a third one. This article focuses on the phenomena of evolution whose appearance is notable because no explicit mutation, recombination, or artificial selection operators are introduced. We call the system self-evolving because every variation is performed by the objects themselves in their machine form.

Artificial Intelligence↗

PubMed2001

The Snail protein family regulates neuroblast expression of inscuteable and string, genes involved in asymmetry and cell division in Drosophila.

Delaminated neuroblasts in Drosophila function as stem cells during embryonic central nervous system development. They go through repeated asymmetric divisions to generate multiple ganglion mother cells, which divide only once more to produce postmitotic neurons. Snail, a zinc-finger transcriptional repressor, is a pan-neural protein, based on its extensive expression in neuroblasts. Previous results have demonstrated that Snail and related proteins, Worniu and Escargot, have redundant and essential functions in the nervous system. We show that the Snail family of proteins control central nervous system development by regulating genes involved in asymmetry and cell division of neuroblasts. In mutant embryos that have the three genes deleted, the expression of inscuteable is significantly lowered, while the expression of other genes that participate in asymmetric division, including miranda, staufen and prospero, appears normal. The deletion mutants also have much reduced expression of string, suggesting that a key component that drives neuroblast cell division is abnormal. Consistent with the gene expression defects, the mutant embryos lose the asymmetric localization of prospero RNA in neuroblasts and lose the staining of Prospero protein that is normally present in ganglion mother cells. Simultaneous expression of inscuteable and string in the snail family deletion mutant efficiently restores Prospero expression in ganglion mother cells, demonstrating that the two genes are key targets of Snail in neuroblasts. Mutation of the dCtBP co-repressor interaction motifs in the Snail protein leads to reduction of the Snail function in central nervous system. These results suggest that the Snail family of proteins control both asymmetry and cell division of neuroblasts by activating, probably indirectly, the expression of inscuteable and string.

Animals↗

PubMed1991

Same-different judgments of multiletter strings: insensitivity to positional bias and spacing.

Several recent studies of multiletter matching have included pairs of strings that have the same letters in different positions (rearranged pairs). The task can be defined such that these rearranged pairs are correctly classified as different (i.e., subjects respond "same" only if the strings have the same letters in the same positions--the order task) or as same (i.e., subjects respond "same" if the strings have the same letters regardless of their positions--the item task). The order task produces left-to-right serial-position effects, whereas the item task produces U-shaped serial-position effects. Because these differences suggest that subjects may be able to exert strategic control over the comparison process, two sets of experiments were designed to test whether or not subjects can change the relative weightings devoted to the respective serial positions. In Experiments 1 and 2, the probability that a mismatch occurred in the different positions was manipulated. In Experiments 3 and 4, the physical spacing between letters, as well as whether or not the spaces were filled with neutral noise characters, was varied. None of the manipulations had much influence on the serial-position effects. Thus, the distinct serial-position effects for the order and item tasks apparently are mandatory and not due to any voluntary comparison strategy.

Attention↗

PubMed1991

Performance tests of Doppler ultrasound equipment with a string phantom.

A detailed testing protocol has been developed for string phantom quality assessment performance measurements of Doppler equipment. General procedures have been developed for accurate setup of the string phantom prior to measurements, independent calibration of the string velocity, and compensation for degassed water in the tank. Detailed testing procedures were developed for important Doppler parameters. The dependence of spectral broadening on Doppler angle is demonstrated and a procedure given for minimizing its effect on Doppler velocity measurements. Doppler velocity calibration to better than 4% has been demonstrated even with degassed water in the tank with six high quality commercial pulsed Doppler systems.

Calibration↗

PubMed2000

The string phenomenon: an important cause of internal mammary artery graft failure.

Internal mammary arteries are the grafts of choice for coronary artery bypass because they are generally free of atherosclerosis and they have high patency rates as grafts. There are, however, increasing reports of graft failure due to diffuse or distal narrowing, known as the string phenomenon. From June 1999 to October 1999, we prospectively reviewed all cases of internal mammary artery angiography at our institution. Twenty-eight cases of internal mammary artery graft failure were identified (M:F, 15:13; mean age, 62 years) out of 261 patients who had undergone internal mammary artery grafting at any institution, including ours. The mean interval between coronary artery bypass and re-angiography was 35 months. There was evidence of competitive flow in 81% (22 of 27) of patients whose internal mammary grafts had developed the string sign. This observational study supports the hypothesis that competitive flow predisposes internal mammary grafts to the string phenomenon. Given the high frequency of competitive flow situations amongst patients with internal mammary artery graft failure, caution should be exercised in the anastomosis of the internal mammary artery to recipient vessels that are less than severely stenosed.

Cineangiography↗

PubMed2001

Scanning electron microscopy determination of string mozzarella cheese in gastric contents.

As part of a suspected homicide investigation, a sampling of the gastric contents from the victim was forwarded to the U.S. Food and Drug Administration's Forensic Chemistry Center (FCC) for analysis of specific, selected components. The victim was known to have consumed string mozzarella cheese, as a snack, less than 24 h before his disappearance and the subsequent discovery of the body. The investigation sought to confirm or dismiss speculation the victim may have been fed a meal or eaten additional food prior to his death. Analysis of the stomach contents involved examination by stereoscopic light microscopy (SLM) and isolation, processing, and analysis of suspect materials by scanning electron microscopy (SEM). Several wax-like, off-white to cream-colored objects were noted by SLM examination and removed from the gastric contents. Through a series of fixation, sectioning, drying, and coating steps, these objects were prepared for analysis by SEM. Comparison of the suspect material with laboratory control string mozzarella cheese showed excellent correlation between the analyzed samples, confirming the suspect material from the stomach contents as string mozzarella cheese.

Cheese↗