Snap Back Research Articles

Sound production mechanism in carapid fish: First example with a slow muscle

Fish sonic swimbladder muscles are the fastest muscles in vertebrates and have fibers with numerous biochemical and structural adaptations for speed. Carapid fishes produce sounds with a complex swimbladder mechanism including skeletal components and extrinsic sonic muscle fibers with an exceptional helical myofibrillar structure. To study this system we stimulated the sonic muscles, described their insertion and action, and generated sounds by slowly pulling the sonic muscles. We find the sonic muscles contract slowly, pulling the anterior bladder and thereby stretching a thin fenestra. Sound is generated when the tension trips a release system that causes the fenestra to snap back to its resting position. The sound frequency does not correspond to the calculated resonant frequency of the bladder, and we hypothesize that it is determined by the snapping fenestra interacting with an overlying bony swimbladder plate. To our knowledge this tension release mechanism is unique in animal sound generation.

Sound production mechanism in carapid fish: first example with a slow sonic muscle

Fish sonic swimbladder muscles are the fastest muscles in vertebrates and have fibers with numerous biochemical and structural adaptations for speed. Carapid fishes produce sounds with a complex swimbladder mechanism, including skeletal components and extrinsic sonic muscle fibers with an exceptional helical myofibrillar structure. To study this system we stimulated the sonic muscles, described their insertion and action and generated sounds by slowly pulling the sonic muscles. We find the sonic muscles contract slowly, pulling the anterior bladder and thereby stretching a thin fenestra. Sound is generated when the tension trips a release system that causes the fenestra to snap back to its resting position. The sound frequency does not correspond to the calculated resonant frequency of the bladder, and we hypothesize that it is determined by the snapping fenestra interacting with an overlying bony swimbladder plate. To our knowledge this tension release mechanism is unique in animal sound generation.

A Static Analysis of Snap Back in the Cantilever with Mems Adhesion

The “Snap back” problem of the micro‐cantilever remains one of the dominant failure mechanisms in the Micro Electro‐mechanical System (MEMS). By analyzing the Hamaker micro continuum medium and solid physics principle, the consistency model of Wigner‐Seitz (W‐S) continuum medium is presented. The gap revision coefficients of the body with the face‐centered cubic structure are derived, which include the attractive force and the repulsive one. The adhesion model of the 500 µ m X 1 µ m silicon micro‐cantilever coated by Au is established. The micro‐cantilever static relationship between the elastic force and the adhesion force is discussed. The reason of the microcantilever “snap back” problem, an instable balanced point, is discovered. Increasing the rigidity of the micro‐cantilever, a method to avoid the micro‐cantilever “snap back” to happen, is put forward, which improves MEMS structure design and enhances MEMS reliability.

A simplified analysis of interface failure under compressive normal stress and monotonic or cyclic shear loading

Interface damage and delamination is usually accompanied by frictional slip at contacting interfaces under compressive normal stress. The present work is concerned with an analysis of progressive interface failure using the cohesive crack model with the critical stress softening and frictional traction present at the contact. Both monotonic and cyclic loadings are considered for anti-plane shear of an elastic plate bonded to a rigid substrate by means of cohesive interface. An analytical solution can be obtained by neglecting the effect of minor shear stress component. The analysis of progressive delamination process revealed three solution types, namely: short, medium and long plate solutions. The long plate solution was obtained under an assumption of quasistatic progressive growth of the delamination zone. In view of snap back response, the quasistatic deformation process cannot be executed by either traction or displacement control. The states of frictional slip accompanied by shake down or incremental failure are distinguished in the case of cyclic loading, related to load amplitude and structural dimensions. The analysis provides a reference solution for numerical treatment of more complex cases. Copyright © 2005 John Wiley & Sons, Ltd.

Electrostatic discharge effects in AlGaN/GaN high-electron-mobility transistors

We investigate 50 μm gate width/0.45 μm length AlGaN/GaN high-electron-mobility transistors (HEMTs) subjected to 100 ns long current pulses that simulate an electrostatic discharge. After source–drain breakdown at around 90 V, the pulsed I–V source–drain characteristic is S shaped with an abrupt snap back to about 20 V at stress current of Istress=0.2 A. Backside interferometric thermal mapping of the HEMT shows that current filamentation accompanies the transition to the low-voltage/high-current region. The shift in transistor threshold voltage is explained by electron trapping in the buffer. It is assumed that breakdown in the regime of electrostatic discharge can be explained as an avalanche-injection event that forms a current filament through the device buffer layer.

Snapping plicae associated with radiocapitellar chondromalacia

Purpose: Painful snapping of the elbow joint is usually attributed to intra-articular loose bodies, instability, or medial dislocation of the triceps muscle over the medial epicondyle. We report our experience with 14 patients who were treated arthroscopically for snapping elbow that was found to be caused by hypertrophic synovial folds associated with radiocapitellar chondromalacia. Type of Study: Case series. Methods: The records of 14 patients who were treated arthroscopically for painful snapping elbows caused by intra-articular plicae were reviewed. There were 6 women and 8 men with an average age of 36 years (range, 27 to 48 years). Nine patients had had some type of trauma to the joint. Four patients had been previously diagnosed with lateral epicondylitis and 5 with intra-articular loose bodies. The average time from initial onset of symptoms to treatment was 13 months (range, 8 to 36 months). Average follow-up was 24 months (range, 6 to 66 months). Results: All patients complained of painful snapping in the posterolateral or anterolateral aspect of the elbow. The snapping occurred between 90° and 110° of flexion with the forearm in pronation. In 7 patients, the snapping was reproducible by passively flexing the pronated elbow, which we refer to as the flexion-pronation test. At the time of arthroscopic surgery, all patients had a thickened synovial plica that would snap back and forward over the radial head, usually associated with a chondromalacic area on the radial head. Twelve patients had complete relief of their snapping after surgery. One patient in whom there was associated posterolateral rotatory elbow instability did not improve. One patient became asymptomatic for 4 years but then had recurrence of her symptoms, which persisted despite 2 subsequent arthroscopies. Conclusions: The presence of synovial plicae in the radiocapitellar joint must be considered in the differential diagnosis of painful snapping elbow. Arthroscopy confirms the diagnosis and allows excision of the plica.Arthroscopy: The Journal of Arthroscopic and Related Surgery, Vol 17, No 5 (May-June), 2001: pp 491–495

Dangers inherited in shells optimized with linear assumptions

This paper provides the background theory and results of an investigation into the dangers inherited in the shells optimized using linear elastic, small displacement, Reissner–Mindlin shell models with shape and/or size design variables. The various tools developed and utilized in this study are briefly described and include computational geometric modelling, automatic mesh generation, finite element analysis, design sensitivity analysis and mathematical programming procedures. In the subsequent studies, once the optimal shape and thickness distributions of the shell have been determined, the non-linear buckling loads of the initial and optimized shells are investigated using a geometrically non-linear analysis tool capable of dealing with complex load–displacement paths including snap-through and snap back.

Novel mutation in the myelin protein zero gene in a family with intermediate hereditary motor and sensory neuropathy

OBJECTIVESTo determine the molecular basis for autosomal dominant intermediate hereditary motor and sensory neuropathy (HMSN) in a four generation family. The gene defects in families with intermediate HMSN are not...

Dynamic snap-back induced programming failure in stacked gate flash EEPROM cells and efficient remedying technique

A new kind of programming failure is reported in stacked gate Flash EEPROM cells and its remedying scheme is presented. The failure is observed under typical bit line (B/L) disturbance bias conditions but is different from the case of the drain turn-on induced leakage current over-burdening the charge pumping. Rather, its root cause is identified for the first time to be the dynamic snap back breakdown operative in the memory cell. This snap-back induced programming failure is shown effectively mitigated with the use of an appropriate series resistance in the source loop of the memory cell. The remedying role of the source series resistance is discussed.

Dual-Gate Shorted Anode SOI Lateral Insulated Gate Bipolar Transistor Suppressing the Snap-Back

A new dual gate shorted anode silicon on insulator (SOI) lateral insulated gate bipolar transistor (LIGBT), which suppresses effectively the snap back without sacrificing the forward voltage drop, the switching speed and the breakdown voltage, is proposed and verified by numerical simulation. The numerical simulation results show that the snap-back is reduced less than the anode voltage of 2.5 V while the snap-back occurs at anode voltage of about 4 V for the conventional structure with the drift length of 35 µ m. We have verified that the snap-back is suppressed due to the enhancement of the hole injection and investigated the snap-back as a function of the device parameters such as the n- drift region doping concentration and drift region length.

Accurate measurement of psoralen-crosslinked DNA: Direct biochemical measurements and indirect measurement by hybridization

This paper evaluates methods to measure crosslinkage due to psoralen plus light in total DNA and in specific sequences. DNA exposed in cells or in vitro to a bifunctional psoralen and near ultraviolet light accumulates interstrand crosslinks. Crosslinkage is the DNA mass fraction that is attached in both strands to a crosslink. We show here biochemical methods to measure psoralen photocrosslinkage accurately in total DNA. We also describe methods to measure photocrosslinkage indirectly, in specific sequences, by nucleic acid hybridization. We show that a single 4,5′,8-trimethylpsoralen (TMP) crosslink causes at least 50 kbp of alkali-denatured DNA contiguous in both strands with it to snap back into the duplex form when the denatured preparation is returned to neutral pH. This process was so efficient that the DNA was not nicked by the singlestrand nuclease S1 at 100-fold excess after snapping back. Uncrosslinked DNA was digested to acid-soluble material by the enzyme. Crosslinkage therefore equals the fraction of S1-resistant nucleotide in this kind of experiment. We alkali-denatured DNA samples crosslinked to varying degrees by varying TMP concentration at constant light exposure. We then measured crosslinkage by ethidium bromide (EtBr) fluorometry at pH 11.8; by EtBr fluorometry at neutral pH of S1 digests of the DNA; and by the fraction of radioactivity remaining acid insoluble in S1-digests of DNA labeled uniformly with [ 3H]deoxythymidine. These assays measure distinct physical properties of crosslinked DNA. Numerical agreement is expected only when all three measurements are accurate. Under optimum conditions, the three methods yielded identical results over the range of measurement. Using alkaline EtBr fluorescence in crude cell lysates, we detected crosslinks at frequencies in the range of 1.6 × 10 −7 per base pair. These levels were compatible with cell survival, attesting to the sensitivity of the measurement system. Crosslinkage affected hybridization as well. One crosslink prevented all alkali-denatured DNA contiguous in both strands with it from hybridizing to complementary DNA either on solid supports or in solution. Strand-length effects on crosslinkage and on reassociation caused solution hybridization levels to exceed those predicted by simple theory. In a quantitative, dot-blotting assay hybridization was linear up to membrane saturation by denatured, uncrosslinked DNA of any strand length. Longer, duplex DNA bound to the membrane, although it hybridized less than 0.03 as efficiently as single-stranded DNA and had no effect on the ability of the latter to bind or hybridize, even when present in great excess. The results here provide the basis for an accurate system to quantify TMP crosslinkage in specific sequences and in total DNA.

Analysis of two-way snap of shells of revolution

The problem of determining the snap and snap back pressures of thin shallow shells of revolution subject to uniform loading is considered. The deformation is modelled using Marguerre's equations and bifurcation and postbuckling analyses are undertaken. A finite element model of the deformation is given and results for snap and snap back are presented.

The anatomy and pathogenesis of wrinkles.

The anatomy of linear wrinkles ("crow's feet' and temporal frown lines), fine criss-cross wrinkles of the face and wrinkling of the general body surface of elderly persons, was studied by light and scanning electron microscopy. No histological features distinguished the various wrinkles from surrounding skin. It was concluded that the wrinkle is a configuration change, like the grooves worn into an old glove, without specific structural alterations at the histological level. As regards pathogenesis, the common setting was found to be deterioration of the elastic tissue network. The skin becomes looser, excessive, and loses the ability to snap back to its original state after being deformed.

Terminal crosslinking of vaccinia DNA strands by an in vitro system

An in vitro system has been developed to study the formation of crosslinks in vaccinia DNA. Cytoplasmic extracts from virus-infected cells were used as a source of activity to catalyze the crosslinking of DNA molecules. Replicating vaccinia DNA lacking crosslinks was used as substrate for the reaction. Sedimentation analysis, hydroxylapatite chromatography, labeling of the free ends, and digestion with restriction endonucleases showed that these molecules were not crosslinked. The conditions of the crosslinking reaction were similar to those required for the activities of the DNA polymerase and polynucleotide ligase in vaccinia-infected cells. The product of the reaction was analyzed by sedimentation in alkaline sucrose gradients and by hydroxylapatite chromatography. The results indicated that cytoplasmic extracts from virus-infected cells were able to catalyze the production of DNA molecules sedimenting as the 90 and 106 S species. These molecules upon denaturation “snap back” to a double-stranded conformation as demonstrated by hydroxylapatite chromatography. Removal from the incubation mixture of ATP, Mg 2+, or deoxynucleotides, as well as heating the extract at 100°, prevented the development of crosslinked molecules. When vaccinia DNA labeled at the 3′ or 5′ termini was used as substrate for the reaction, it was shown that loss of radioactivity occurred only at the 3′ termini. Furthermore, after the reaction 5′- 32P-labeled DNA became resistant to alkaline phosphatase implying that the termini were no longer free. Exonuclease, DNA polymerase, and DNA ligase activities were detected in the cytoplasmic extracts of virus-infected cells, suggesting that they may be involved in the crosslinking reaction. Based on the experimental evidence, a model for the formation of crosslinks is proposed.

Yeast chromosomal DNA molecules have strands which are cross-linked at their termini

The microbial eukaryote Saccharomyces cerevisiae has 18 chromosomes, each consisting of a DNA molecule of 1 x 15 x 10(8) daltons (150 to 2,300 kilobase pairs). Interstand cross-links have now been found in molecules of all sizes by examining the ability of high molecular weight DNA to snap back, i.e., to rapidly renature after denaturation. Experiments in which snap back was assessed for molecules broken by shearing indicate that there are probably two cross-links in each chromosome. Evidence that the cross-links occur at specific sites in the genome was obtained by treating total chromosomal DNA with the endonuclease EcoRI which cleaves the yeast genome into approximately 2,000 discrete fragments. Cross-link containing fragments were separated from fragments without cross-links. This purification resulted in enrichment for about 18 specific fragments. To determine whether the cross-links are terminal or at internal sites in chromosomal DNA, large shear-produced fragments were examined by electron microsopy. With complete denaturation few fragments exhibit the X-shaped single strand configuration expected for internal cross-links. When partially denatured fragments were examined some ends had single strand loops as expected for (AT-rich) cross-linked termini. We propose that a duplex chromosomal DNA molecules have cross-linked termini. We propose that a duplex chromosomal DNA molecule in this eukaryote consists of a continuous, single, self-complementary strand of DNA. This structure has implications for the mechanism of chromosome replication and may be the basis of telomere behavior.

Structure changes caused by strain annealing of nylon 6 fibers

Abstract Experiments are described in which nylon 6 fibers are annealed while subjected to a constant stretch (or slack). Subsequent mechanical and structural measurements are described and analyzed. A paracrystalline structure model is proposed in which folded chains, fully extended chains, partially folded, and partially extended chains coexist in the highly drawn high strength fiber. An explanation of structural changes occurring during the thermal-mechanical treatment is that the folded and partially folded chains are arranged randomly in staggered fashion in small units throughout the structure. During slack annealing, the chains become more folded and shrinkage occurs. Some of the chain refolding will be permanent and may act as new defect sites thereby reducing fracture stress. During annealing in the presence of comparatively high tensile stresses the folded chains are unfolded to some extent, but not completely, and the load-carrying chains in the structure are more uniformly loaded. At the higher applied strains during annealing, chains are broken and may snap back into folds. The tension annealing increases the overall chain orientation, the strained segment uniformity, and the number of load-bearing chains. These factors may contribute to an increased fracture stress.

Excision of DNA segments introduced into cloning vectors by the poly(dA-dT) joining method.

A method is described for excising cloned DNA segments that have been inserted into their vectors by poly(dA-dT) joins. The recombinant DNA is cleaved within the vector DNA portion by one or more restriction endonucleases to generate a linear DNA molecule with the insert DNA sequence flanked by the poly(dA-dT) joins. After denaturation, the single strands "snap back" because of the intrastrand poly(dA) and poly(dT) sequences to form circular structures with "tails" of vector DNA. The vector portion of the DNA is then digested by Escherichia coli exonuclease VII, while the insert portion remains resistant to attack. The resistant strands are annealed and purified by electrophoresis in agarose. The insert DNA segment free of contaminating vector sequences can be used as a hybridization probe and for insertion into a new vector since suitable cohesive termini are generated from the retained poly(dA) and poly(dT) tails by an appropriate exonuclease.

‘MAGIC MEMORY METALS’ SNAP BACK TO SAVE LIVES

School Science and MathematicsVolume 77, Issue 3 p. 188-188 ‘MAGIC MEMORY METALS’ SNAP BACK TO SAVE LIVES First published: March 1977 https://doi.org/10.1111/j.1949-8594.1977.tb09335.xCitations: 2AboutPDF ToolsRequest permissionExport citationAdd to favoritesTrack citation ShareShare Give accessShare full text accessShare full-text accessPlease review our Terms and Conditions of Use and check box below to share full-text version of article.I have read and accept the Wiley Online Library Terms and Conditions of UseShareable LinkUse the link below to share a full-text version of this article with your friends and colleagues. Learn more.Copy URL Share a linkShare onFacebookTwitterLinked InRedditWechat No abstract is available for this article.Citing Literature Volume77, Issue3March 1977Pages 188-188 RelatedInformation

Characterization and localization of the naturally occurring cross-links in vaccinia virus DNA

The vaccinia virus genome is a single, linear, duplex DNA molecule whose complementary strands are naturally cross-linked. The molecular weight has been determined by contour length measurements from electron micrographs to be 122 ± 2.2 × 10 6. Denaturation mapping techniques indicate that the nucleotide sequence arrangement of the DNA is unique. Two forms of cross-linked vaccinia DNA were observed in alkaline sucrose gradients. The relative S-values of the two cross-linked species were appropriate for a single-stranded circle and a linear single strand, each with a molecular weight twice that expected for an intact, linear, complementary strand of vaccinia DNA. The fraction of sheared vaccinia DNA able to “snap back” after denaturation suggested a minimum of two crosslinks per molecule. Full-length single-stranded circles were observed in the electron microscope after denaturation of vaccinia DNA. Partial denaturation produced single-stranded loops at the ends of all full-length molecules. Exposure of native vaccinia DNA to a single strand-specific endonuclease isolated from vaccinia virions caused disruption of the cross-links, as assayed by alkaline sedimentation, and produced free single-strand ends when partially denatured DNA was observed in the electron microscope. We conclude that vaccinia DNA contains two cross-links, one at or near (within 50 nucleotides) each end in a region of single-stranded DNA. Two models for the cross-links are presented.

The Dynamics of Roller Drafting

A description is given of the design and operation of a drafting force tester, with emphasis on the material and process variables which influence test results. Visual observations are reported of sliver contraction, fiber straightening, and fiber snap back. Comparison is made between the force-deformation behavior of a sliver in steady-state drafting, in an arrested-back-roller drafting test and in a conventional Instron tensile test. The deformation behavior is characterized by fiber extension, sliver consolidation, and force buildup, followed by fiber slippage and force decline. The effect of surface roughness is investigated for various test configurations. Other specific variables studied were roller separation, draft ratio, fiber crimp, and sliver processing history.