Twist Pattern Research Articles

A New Coding System for the Identification of Left Ventricular Rotation Patterns and Their Relevance to Myocardial Function

Rotational mechanics is a fundamental determinant of left ventricular ejection fraction (LVEF). The coding system currently employed in clinical practice does not distinguish between rotational patterns. We propose an alternative coding system that makes possible to identify the rotational pattern of the LV and relate it to myocardial function. Echocardiographic images were used to generate speckle tracking-derived transmural global longitudinal strain (tGLS) and rotational parameters. The existence of twist (basal and apical rotations in opposite directions) is expressed as a rotational gradient with a positive value that is the sum of the basal and apical rotation angles. Conversely, when there is rigid rotation (basal and apical rotations in the same direction) the resulting gradient is assigned a negative value that is the subtraction between the two rotation angles. The rotational patterns were evaluated in 87 healthy subjects and 248 patients with LV hypertrophy (LVH) and contrasted with their myocardial function. Our approach allowed us to distinguish between the different rotational patterns. Twist pattern was present in healthy controls and 104 patients with LVH and normal myocardial function (tGLS ≥ 17%, both). Among 144 patients with LVH and myocardial dysfunction (tGLS < 17%), twist was detected in 83.3% and rigid rotation in 16.7%. LVEF was < 50% in 34.7%, and all patients with rigid rotation had a LVEF < 50%. The gradient rotational values showed a close relationship with LVEF (r = 0.73; p < 0.001). The proposed coding system allows us to identify the rotational patterns of the LV and to relate their values with LVEF.

Propagation characteristics of twisted cosine-Gaussian Schell-model beams

We introduce a new class of twisted sources with twisted cosine-Gaussian Schell-model correlation structure. The spectral intensity and the degree of coherence of the field upon propagation are discussed. Such novel twisted field is characterized by unfamiliar twist pattern and controllable far-zone lattice profile. It exhibits a Gaussian or a lattice-like intensity distribution in the source plane, while always turns into a 2×2 lattice profile in the far zone. Notably, the array profile twists around the propagation axis instead of each element rotating about its own lobe center, which is different from most of the twisted array models. Moreover, the splitting tendency in the intensity distribution could be flexibly modulated by the twisted factor, the source coherence and the beam width. The coherence distribution could rotate in the same direction as the intensity with appropriate choice of parameters. Finally, the cross-spectral density’s phase distribution exhibits a spiral windmill structure and coherent singularities could be observed upon propagation.

Hexagonal Twist Origami Pattern for Deployable Space Arrays

Abstract The hexagonal twist origami pattern has characteristics that made it a candidate for next-generation deployable space arrays. It has a deployed area that is up to 3.3 times larger than the stowed area, has a single-degree-of-freedom which simplifies actuation, it is flat-foldable making flat positions possible in both stowed and deployed positions, and its rigid foldability means that its motion is enabled by rotation about distinct axes without deformation of its panels. Although the pattern shows promise for deployable systems, it cannot be directly applied with thick materials because of the self-intersection of nesting panels. This paper presents the kinematics and mechanical advantages of the hexagonal twist pattern, addresses the self-intersection problem by implementing five different thickness accommodation techniques and provides metrics for comparing thickness accommodation techniques to determine which would be best suited for a given application. The concepts are demonstrated through two applications: a deployable reflectarray antenna and a LiDAR telescope.

Twisted loxodromes in spindle-shaped polymer nematics.

We develop an energetic model that captures the twisting behavior of spindle-shaped polymer microparticles with nematic ordering, which display remarkably different twisting behavior to ordinary nematics confined to spindles. We have previously developed a geometric model of the twisting, based on experimental observations, in which we showed that the twist pattern follows loxodrome spirals [Ansell, et al., Phys. Rev. Lett., 2019, 123, 157801]. In this study, we first consider a spindle-shaped surface and show that the loxodrome twisting behavior of our system can be captured by the Frank free energy of the nematic with an additional term constraining the length of the integral curves of the system. We then extend the ideas of this model to the bulk and explore the parameter space for which the twisted loxodrome solution is energetically favorable.

Association between the morphometric parameters of placenta and umbilical cord with the birth weight

Objectives: Birth weight is a vital parameter used to predict the future growth and development of a new born. The survival of the foetus in utero depends on proper functions of the placenta. The study aims to express the relation between the birth weight and placental and umbilical cord morphometric parameters. Materials and methods: The study was conducted on 418 singleton normal vaginal deliveries. The collected placentae were washed to remove the blood clots and the weight, thickness, and diameters of placentae and the length of umbilical cord were measured. Shape and margin of the placentae, location of umbilical cord insertion and number of cotyledons and the twist pattern of umbilical cord have been determined through careful examination. the birth weight of the foetus was obtained immediately after the delivery. Results: The collected data has been analysed by multiple linear regression test using R software with p value ≤ 0.05 as the significance. The weight of the foetus exhibited positive significant linear relationship with thickness (p=0.001), weight (p=0.000) and Surface area (p=0.000) of the placental disk. The velamentous cord insertion showed (p=0.019) negative relation with birth weight. The non-twist umbilical cord showed positive significant (p=0.04) association with birth weight. Other parameters were not significant with the birth weight. Conclusion: Thickness, weight and surface area of the disk and non-twist umbilical cord increases the birth weight of the foetus. However, velamentous cord insertion related to reduction in the birth weight.

Echocardiographic characteristics of patients with SARS-CoV-2 infection

BackgroundMyocardial involvement induced by SARS-CoV-2 infection might be important for long-term prognosis. The aim of this observational study was to characterize the myocardial effects during SARS-CoV-2 infections by echocardiography.Results and methodsAn extended echocardiographic image acquisition protocol was performed in 18 patients with SARS-CoV-2 infection assessing LV longitudinal, radial, and circumferential deformation including rotation, twist, and untwisting. Furthermore, LV deformation was analyzed in an age-matched control group of healthy individuals (n = 20). The most prevalent finding was a reduced longitudinal strain observed predominantly in more than one basal LV segment (n = 10/14 patients, 71%). This pattern reminded of a “reverse tako-tsubo” morphology that is not typical for other viral myocarditis. Additional findings included a biphasic pattern with maximum post-systolic or negative regional radial strain predominantly basal (n = 5/14 patients, 36%); the absence or dispersion of basal LV rotation (n = 6/14 patients, 43%); a reduced or positive regional circumferential strain in more than one segment (n = 7/14 patients, 50%); a net rotation showing late post-systolic twist or biphasic pattern (n = 8/14 patients, 57%); a net rotation showing polyphasic pattern and/or higher maximum net values during diastole (n = 8/14 patients, 57%).ConclusionMyocardial involvement due to SARS-CoV-2-infection was highly prevalent in the present cohort—even in patients with mild symptoms. It appears to be characterized by specific speckle tracking deformation abnormalities in the basal LV segments. These data set the stage to prospectively test whether these parameters are helpful for risk stratification and for the long-term follow-up of these patients.

Truss-based nonlinear mechanical analysis for origami structures exhibiting bifurcation and limit point instabilities

Origami, the art of paper folding, is a technologically transformative art with applications at many length scales from material microstructure design to space deployable structures. The transformation of a two-dimensional fold pattern to a three-dimensional structure makes origami a practical basis for deployability, light-weight materials, and self-actuation. In order to predict the complex motions of origami structures including path traversal of instabilities, accurate and efficient modeling techniques are required. While many approaches consider rigid facets and/or linear approximations to rotations, a truss and hinge finite element method is presented here within a global coordinate system framework to accurately capture the geometric nonlinearities while allowing for small to moderate facet deformation. Accurately capturing these modes of deformation is critical toward understanding the elastic energetic states required for design and analysis of multistable origami structures and mechanical metamaterials. Particular formulation developments that we address to solve origami mechanics problems include formulation of a continuous and differentiable fold angle, strategy for selecting fold path off the flat state, and integration of common numerical approaches important for origami (large rotation formulation, enforcement of periodic boundary conditions for tessellations, arc-length continuation method for solving highly nonlinear loading paths, and a perturbation strategy for handling bifurcations). After formulating this truss finite element method, we verify our modified finite element method on well-studied structures. The waterbomb fold pattern is studied, and the interplay of the stretching and folding energies are considered toward design of a bistable structure that exhibits a fold based snap-through instability. This study is followed by analysis of a cylindrical network of waterbombs (axial periodicity) that exhibits a stretch driven instability. Lastly, a tessellated square twist pattern, exhibiting multiple bifurcations off the flat state is presented that employs all aspects of our numerical method.

Analysis of micro-failure behaviors in artificial muscles based on fishing line and sewing thread

The aim of the present study was to discuss a new and effective method for testing artificial muscles based on micro-failure behaviors analysis. Thermo-mechanical actuators based on fishing line and sewing thread, also, the capability of responding to ambient temperature variations producing a large amount of shrinkage ratio of a resulting variation in longitudinal length. The minimum micro-failure value is 0.02μm and the maximum value is 1.72μm with nylon twist pattern. The discovery of an innovative effective testing of artificial muscles based on polymeric fibers specimens on micro-failure, rupture, slippage, etc. This research finds out a micro-failure behavior analysis of thermo-mechanical actuators based on fishing line and sewing thread. The specimens show large deformations when heated together with warping performance in terms of shrinkage of energy and densities. With the purpose of providing useful analysis data for the further technology applications, we attempt micrometre-sized artificial muscles which were also tested was readily accessible and also can be applied to other polymeric fibers. Effective use of this technique achievement relies on rotate speed, temperature and tensile direction. The results of the tensile testing experiments were outstanding with respect to some important issues related to the response of micro-structure, twisted polymeric fibers and shrinkage ratio.

Significance of twist and iNOS expression in human breast carcinoma.

Twist is a basic helix-loop-helix transcription factor family normally expressed during embryonic development and apparently activated in variety of tumours. Overexpression of twist is correlated with uncontrolled cell proliferation, differentiation, invasion and metastasis. Twist expression is associated with oestrogen receptor (ER); however, the molecular mechanism behind involvement of twist in progression of breast cancer is still unclear. Nitric oxide synthases (NOSs) which cause damage to the cellular DNA are also shown to be involved in cancer progression. The present study involves total number of n = 85 breast biopsies, which include 19 non-cancer and 66 cancerous lesions. We analysed twist, iNOS and ER expression pattern in human breast carcinomas by RT-PCR and also analysed twist cellular localisation by immunohistochemical analysis. iNOS expression pattern was correlated with different stages of breast carcinoma. Twist expression was significantly increased in cancer lesions when compared to the non-cancer. The breast cancer lesions positive to ER showed positivity to twist (72%) as well. The higher stages of cancer lesions showed a significant expression of twist localised in cytoplasm of the cancer cells. Collectively these data indicate that up-regulation of twist is correlated with the ER presenting breast cancer, and iNOS expression was positively correlated with tumour-node metastasis (TNM) staging of breast cancer. These findings suggest that expression of twist and iNOS may have a functional role in cancer progression.

Structural similarity of wild-type and ALS-mutant superoxide dismutase-1 fibrils using limited proteolysis and atomic force microscopy

Abnormal assemblies formed by misfolded superoxide dismutase-1 (SOD1) proteins are the likely cause of SOD1-linked familial amyotrophic lateral sclerosis (fALS) and may be involved in some cases of sporadic ALS. To analyze the structure of the insoluble SOD1 amyloid fibrils, we first used limited proteolysis followed by mass spectrometric analysis. Digestion of amyloid fibrils formed from full-length N-acetylated WT SOD1 with trypsin, chymotrypsin, or Pronase revealed that the first 63 residues of the N terminus were protected from protease digestion by fibril formation. Furthermore, every tested ALS-mutant SOD1 protein (G37R, L38V, G41D, G93A, G93S, and D101N) showed a similar protected fragment after trypsin digestion. Our second approach to structural characterization used atomic force microscopy to image the SOD1 fibrils and revealed that WT and mutants showed similar twisted morphologies. WT fibrils had a consistent average helical pitch distance of 62.1 nm. The ALS-mutant SOD1 proteins L38V, G93A, and G93S formed fibrils with helical twist patterns very similar to those of WT, whereas small but significant structural deviations were observed for the mutant proteins G37R, G41D, and D101N. Overall, our studies suggest that human WT SOD1 and ALS-mutants tested have a common intrinsic propensity to fibrillate through the N terminus and that single amino acid substitutions can lead to changes in the helical twist pattern.

Time to twist: marker of systolic dysfunction in Africans with hypertension

Speckle-tracking echocardiography (STE) has emerged as a quantitative technique to assess left ventricular (LV) function via twist mechanics. Hypertension-associated changes in LV twist have not been previously evaluated in African patients with LV systolic dysfunction. This study evaluates LV twist dynamics in hypertensive patients with a low ejection fraction (EF). Forty-one hypertensive patients with EF <45% and normal coronary angiography (HTLEF group) were compared with 41 control subjects using STE. Peak apical rotation (AR) and isochronous basal rotation (BR) were measured, as was net twist (maximal value of simultaneous AR-BR). Rigid body rotation (RBR) was defined as AR and BR occurring in the same direction. Of 41 HTLEF patients, 28 (68%) had normal twist pattern, whereas 13 (32%) exhibited RBR; 11 of those 13 exhibited clockwise rotation. AR (1.89° ± 0.99 vs. 7.15° ± 2.26; P < 0.0001), BR (1.44° ± 0.78 vs. -3.75° ± 1.61; P < 0.0001), and net twist (3.3° ± 1.17 vs. 10.9° ± 2.7; P < 0.0001) were lower in HTLEF patients. The subgroup with clockwise RBR showed greater LV dysfunction (EF: 27.9 ± 5.8 vs. 35 ± 7.5%; P = 0.005) and more spherical LV geometry in both diastole and systole (P = 0.0009 and P = 0.0002, respectively) compared with those who had a normal pattern of twist. In the HTLEF subgroup with normal twist pattern, AR (r = 0.57; P = 0.002) and net twist (r = 0.57; P = 0.002) correlated with EF. LV twist in patients with hypertension and EF <45% is diminished. Apical rotation and net twist are good correlates for EF in hypertensive patients with EF <45%.

Assessment of cardiac twist in dilated cardiomyopathy using echocardiography velocity vector imaging

To assess cardiac twist in dilated cardiomyopathy (DCM) patients using echocardiography velocity vector imaging (VVI) and to explore the clinical application value of VVI in evaluating cardiac twist. Thirty-three normal subjects and 30 DCM patients were enrolled. Echocardiographs of parasternal left ventricle basal, papillary muscle level and apical short axis plane, apical four-, two-chamber plane were obtained respectively. Systolic maximal rotation degree, peak rotation velocity, circumferential strain (CS), time to peak rotation velocity (TPRV), peak un-rotation velocity of end diastole and end isovolumic relaxation period in subendocardium were measured by VVI software. (1) In the normal group, left ventricle performed systolic wring motion with counterclockwise rotation at the apex and clockwise rotation at the base as seen from the apex, while with transient counterclockwise rotation at the base and clockwise rotation at the apex in isovolumic relaxation period. The papillary level rotation form was not constant For the dominant rotation action of the apex, the whole cardiac twist form was counterclockwise. (2) Compared with the control group, 4 DCM patients cardiac twist pattern changed: two showed both counterclockwise rotation of the base and the apex, one represented both clockwise rotation of the base and the apex, another performed the base rotated counterclockwise and the apex rotated clockwise. (3) All rotation and twist parameters of other 26 DCM patients decreased, especially at the apical level: LVtw:7.34 degrees +/- 3.65 degrees vs. 17.01 degrees +/- 4.81 degrees, LVtor: (0.09 +/- 0.04) degrees/mm vs. (0.23 +/- 0.06) degrees/mm, torsion rate: (60.23 +/- 23.67) degrees/s vs. (148.24 +/- 56.23) degrees/s, untwisting rate (0.37 +/- 0.19) degrees/m vs. (0.59 +/- 0.33%)/m, basal CS: (-8.09 +/- 2.73)% vs. (-19.49 +/- 5.51)% (P = 0.013), apical CS: (-8.94 +/- 5.90)% vs. (-27.49 +/- 9.53)% (P = 0.000), basal rotation angle: (-3.60 +/- 2.38) vs. (-6.28 +/- 3.05) (P = 0.014), apical rotation angle: (5.80 +/- 3.55) degrees vs. (11.02 +/- 3.33) degrees (P = 0.001). (4) The apical TPRV in DCM group were longer than the control group represented rotational dyssynchrony in DCM patients (400.26 ms +/- 70.15 ms vs 328.13 ms +/- 66.95 ms, P = 0.008). LVtw correlated positively well with EF (r = 0.489, P < 0.05). (1) Cardiac twist function was diffusely impaired in DCM patients and it contributed to the global cardiac dysfunction. (2) Cardiac twist pattern changed in some of DCM patients. (3) VVI can objectively reflect cardiac twist function in DCM patients.

First Experimental Evaluation of Cardiac Apex Rotation with an Epicardial Coriolis Force Sensor

Cardiac apex rotation, quantified by sophisticated techniques (radiopaque markers and tagged magnetic resonance), has been shown to provide a sensitive index of left ventricle (LV) dynamics. The authors describe the first experimental assessment of cardiac apex rotation using a gyroscopic sensor based on Coriolis force, epicardially glued on the apex. Dynamics of apex rotation were evaluated in a sheep at baseline, after a positive inotropic drug infusion, and after impairment of cardiac function induced by coronary ligation. To evaluate the efficacy of the sensor to monitor cardiac function, results were compared to contractility variations expressed by the maximum value of the first derivative of LV pressure (LVdP/dtMAX). After inotropic drug infusion, a parallel increasing trend resulted for LVdP/dtMAX, for the maximum value of angular velocity measured by the sensor, and for apex rotation angle derived from velocity signal (+146%, +155%, and +11% from baseline, respectively), whereas a decreasing trend of all three parameters resulted after coronary ligation (-35%, -31%, and -65%). The twist pattern also was altered from baseline. These initial results suggest that the use of an implantable rotation sensor based on Coriolis force can be an efficient and effective tool to assess LV torsional deformation both in normal and failing hearts.

Voltage sensing in ion channels: a 50-year-old mystery resolved?

Membrane-protein ion channels control electrical activity in the nervous system. Voltage-gated channels have four-fold symmetry, with a central pore domain surrounded by voltage-sensor regions. Each voltage-sensor region has a positively charged transmembrane helix, S4, which carries gating charges through the membrane on opening or closing. How S4 moves at gating is debated: either S4 moves in a helical screw or in a helical twist pattern. In both cases S4 is assumed to move inside the densely packed channel protein. The pore region was visualised when Roderick MacKinnon's group crystallised a bacterial K+ channel in 1998. The voltage-sensor region and the S4 movement are more difficult to visualise, because voltage-gated channels are harder to crystallise. Recently, Yuoxing Jiang and colleagues in MacKinnon's group reported the first successful crystallisation and X-ray analysis of a voltage-gated channel (Nature 2003; 423: 33-41, 42-48), with unexpected results. S4 forms a hairpin loop with another helix, stretching out from the channel perimeter rather than being located inside the densely-packed protein core. This finding suggests a novel type of S4 movement at gating, a paddle sweeping through the lipid bilayer in response to voltage changes. WHERE NEXT? Jiang and colleagues' unexpected results are controversial. Several predictions of the model are incompatible with other experimental data. However, if the paddle configuration is real, it opens up a new field for pharmacological rethinking. Such a configuration may help to understand certain aspects of the action of lipid-soluble gating modifiers, such as local and general anaesthetics and antiarrythmic and antiepileptic agents.

Alternation of DNA and Solvent Layers in the A Form of d(GGCGCC) Obtainhted by Ethanol Crystallization

We have determined by X-ray crystallography the structure of the hexamer duplex d(GGCGCC)2 in the A-form using ethanol as a precipitant. The same sequence had previously been crystallized in the B-form, but with 2-methyl-2, 4-pentanediol as a precipitant. It appears that ethanol precipitation is a useful method to induce the formation of A-form crystals of DNA. Packing of the molecules in the crystal has unique features: the known interaction of A-DNA duplexes between terminal base-pairs and the minor groove of neighbor molecules is combined with a superstructure consisting in an alternation of DNA layers and solvent layers (water/ions). This organization in layers has been observed before, also with hexamers in the A conformation which crystallize in the same space group (C222 1). The solvent layer has a precise thickness, although very few ordered water molecules can be detected. Another feature of this crystal is its large unit cell, which gives rise to an asymmetric unit with three hexamer duplexes. One of the three duplexes is quite different from the other two in several aspects: the number of base pairs per turn, the twist pattern, the mean value of the twist angle and the fact that one terminal base-pair is not stacked as part of the duplex and appears to be disordered. So the variability in conformation of this sequence is remarkable.

Dynamics of left ventricular apex rotation during angioplasty: a sensitive index of ischemic dysfunction.

Apex rotation has been shown to provide a reliable index of the dynamics of left ventricular (LV) twist. In this study, we aimed to characterize twist at baseline and during acute ischemia in 20 patients undergoing percutaneous transluminal coronary angioplasty to the left anterior descending (LAD) artery and to test whether an old myocardial infarction or collateral flow affected twist dynamics. Among patients with no previous infarction, five had no collaterals (group A) and six had angiographically visible collaterals (group B). Previous anterior infarction was present in nine patients (group C). Data were acquired with the LAD angioplasty wire passed beyond the apex using a view aligned with the LV long axis. Frame-by-frame dynamics of apex rotation were measured from the angular movement of the portion of the wire that traversed the apex. Aortic pressure recordings allowed precise temporal definition of the cardiac cycle. Dynamics of apex rotation were measured at fixed intervals until 60 seconds of occlusion and up to 60 seconds of reperfusion. In group A, counterclockwise apex rotation (twist) during ejection of -22.0+/-1.7 degrees (mean+/-SEE) was followed by rapid clockwise rotation (untwist) during isovolumic relaxation. During 60 seconds of ischemia, maximum apex rotation decreased to -8.2+/-2.0 degrees (P<.001 versus baseline). In group B, baseline apex rotation was similar (-26.2+/-6.9 degrees) to that in group A, but ischemia had less effect, with apex rotation values of -17.7+/-3.4 degrees (P<.05 versus group A values). Group C was characterized by reduced baseline apex rotation values (-9.7+/-3.1 degrees, P<.05 versus group A values), with little change observed during ischemia (-8.1+/-2.6 degrees). Apex rotation, an index of ventricular twist, is sensitive to acute ischemia in patients without previous myocardial infarction. Visible collaterals to the ischemic region attenuate the acute ischemic response at 60 seconds. Previous myocardial infarction causes abnormalities in the baseline twist pattern with no further deterioration at 60 seconds of ischemia.

The structure of an RNA “kissing” hairpin complex of the HIV TAR hairpin loop and its complement

We have used nuclear magnetic resonance (NMR) to obtain the structure of an RNA “kissing” hairpin complex formed between the HIV-2 TAR hairpin loop and a hairpin with a complementary loop sequence. Kissing hairpins are important in natural antisense reactions; their complex is a specific target for protein binding. The complex has all six nucleotides of each loop paired to form a bent quasicontinuous helix of three coaxially stacked helices: two stems plus a loop-loop interaction helix. Experimental constraints derived from heteronuclear and homonuclear NMR data on 13C and 15N-labeled RNA led to a structure for the loop-loop helix with an average root-mean-square deviation of 0.83 (±0.10) Å for 33 converged structures relative to the average structure. The loop-loop helix of the kissing complex is distorted compared to A-form RNA. Its major groove is blocked by the phosphodiester bonds that connect the first loop residue of each hairpin with its own stem, and it is flanked by two negatively charged phosphate clusters. The loop-loop helix has alternating helical twists between adjacent base-pairs. The base-pairs at the helix junctions are overwound and three base-pairs near the helix junctions adopt high propeller twists. All these changes reduce the distance needed for the bridging phosphodiester bonds connecting each stem and loop to cross the major groove of the loop-loop helix, and result in a deformed RNA helix with localized perturbations in the minor groove surface. The alternating helical twist pattern, plus other distortions in the loop-loop helix may be important for Rom protein recognition of the kissing hairpin complex.

Alterations in left ventricular diastolic twist mechanics during acute human cardiac allograft rejection.

Contraction of obliquely oriented left ventricular (LV) fibers results in a twisting motion of the left ventricle. The purpose of this study was to assess the effects of acute human cardiac allograft rejection on LV twist pattern and the twist-volume relation. Tantalum markers were implanted into the LV midwall in 15 transplant recipients to measure time-varying, three-dimensional chamber twist using computer-assisted analysis of biplane cinefluoroscopic images. Twist was defined as the mean longitudinal gradient of circumferential rotation about the LV long axis. When plotted against normalized percent ejection fraction (%EF), the resulting twist-normalized %EF relation could be divided into three phases. In systole, LV twist was linearly related to ejection of blood. In contrast, diastolic untwist was characterized by early rapid recoil with little change in LV volume, followed by more gradual untwisting when the bulk of diastolic filling occurred. During 10 acute rejection episodes in 10 patients, maximum twist, peak systolic twist rate, and the slope of the systolic twist-normalized %EF relation did not change. In contrast, the slope of the early (first 15% of filling) diastolic twist-normalized %EF relation (M(early-dia)) decreased significantly (-0.194 +/- 0.062 [prerejection] versus -0.103 +/- 0.054 rad/cm [rejection], p = 0.0003), resulting in a prolonged tau 1/2 (time required to untwist by 50% [20 +/- 5% versus 28 +/- 5% of diastole], p = 0.0003) and decrease in percent untwisting at 15% diastolic LV filling (62 +/- 11% versus 36 +/- 13%, p = 0.0003). Therefore, a greater proportion of LV untwisting occurred later in diastole during rejection, as reflected by an increase in the slope (M(mid-dia)) of the middle to late (from 15 to 90% filling) diastolic twist-normalized %EF relation (-0.018 +/- 0.009 versus -0.030 +/- 0.010 rad/cm, p = 0.0015). Peak rate of untwist was not affected. With resolution of rejection, M(early-dia) and percent untwist during early diastole returned to baseline levels (p = NS versus baseline). There was also a trend for M(mid-dia) to return toward prerejection values (p = NS versus baseline), but this change did not reach statistical significance compared with rejection values. Acute cardiac allograft rejection is associated with altered diastolic twist mechanics in the absence of any demonstratable systolic abnormalities. During rejection, myocardial edema and other factors may result in intrinsic changes of the elastic properties of the myocardium, thereby leading to modification of recoil forces responsible for the early, rapid unwinding of the deformed ventricle.

The Effects of Construction on the Wear Wrinkling of Dacron®/Wool Suitings

This paper describes a systematic investigation of the effects of fabric construction on the wear wrinkling of worsted spun "Dacron" polyester/wool blend fabrics. Variables studied were blend ratio, yarn count, yarn twist, yarn ply, fabric tightness, and fabric weave pattern. The effect of these variables on the wrinkle resistance of fabrics was compared in laboratory tests under controlled atmospheric conditions and in carefully monitored slack wear tests. These studies led to the conclusion that the three major construction factors which determine wear wrinkling are the proportion of polyester fibers, the yarn count, and the weave pattern. Best performance resulted from the use of high blend levels, coarse yams, and long-float weaves. While the absolute performance levels can be modified by changing test conditions (humidity, wearer severity, or recovery time), the over-all conclusions are unaltered. Within the limits of this investigation, interfiber friction, yarn twist, and tightness for a given weave and yarn size (weight) had little effect on wrinkle propensity. These findings are generally consistent with accepted mechanical concepts of fabric behavior.