Splay Angle Research Articles

Multicenter CT Image-Based Anatomic Assessment of Patients with Aortoiliac Aneurysm Undergoing Endovascular Repair with Iliac Branch Devices

ObjectiveThe Global Iliac Branch Study (NCT05607277) is an international, multicenter, retrospective cohort study of anatomic predictors of adverse iliac events (AIE) in aortoiliac aneurysms treated with iliac branch devices (IBDs). MethodsPatients with pre- and post-IBD CT imaging were included. We measured arterial diameters, stenosis, calcification, bifurcation angles, and tortuosity indices using a standardized, validated protocol. A composite of ipsilateral AIE was defined, a priori, as occlusion, type I or III endoleak, device constriction, or clinical event requiring reintervention. Paired t-test compared tortuosity indices and splay angles pre- and post-treatment for all IBDs and by device material (stainless steel and nitinol). Two-sample t-test compared anatomical changes from pre- to post-treatment by device material. Logistic regression assessed associations between AIE and anatomic measurements. Analysis was performed by IBD. ResultsWe analyzed 297 patients (286 males, 11 females) with 331 IBDs (227 stainless steel, 104 nitinol). Median clinical follow-up was 3.8 years. Iliac anatomy was significantly straightened with all IBD treatment, though stainless steel IBDs had a greater reduction in total iliac artery tortuosity index and aortic splay angle compared to nitinol IBDs (absolute reduction -.20 [-.22 to -.18] versus -.09 [-.12 to -.06], P<.0001 and -19.6° [-22.4° to -16.9°] versus -11.2° [-15.3° to -7.0°], P=.001, respectively). There were 54 AIEs in 44 IBDs in 42 patients (AIE in 13.3% of IBD systems), requiring 35 reinterventions (median time to event 41 days; median time to reintervention 153 days). There were 18 endoleaks, 29 occlusions, and five device constrictions. There were no strong associations between anatomic measurements and AIE overall, though internal iliac diameter was inversely associated with AIE in nitinol devices (nAIE,nitinol=8). ConclusionsPurpose-built iliac branch devices effectively treat aortoiliac disease, including that with tortuous anatomy, with a high patency rate (91.5%) and low reintervention rate (9.1%) at four years. Anatomic predictors of AIE are limited.

Specialized diving traits in the generalist morphology of Fulica (Aves, Rallidae)

Foot-propelled diving comprises the primary locomotion-based feeding strategy for many birds, including families such as Phalacrocoracidae, Anhingidae, Podicipedidae, Gaviidae, and the diving ducks within Anatidae. While the morphology of specialized divers is well known, the corresponding morphology is less known for birds not as specialized but capable of diving, such as the coots (Rallidae, Fulica spp.). To compare the osteology of Fulica with other (non-diving) Rallidae, and with foot-propelled diving birds that are distantly related, we considered osteological characters, as well as the proportion of the hind limb bones and the femoral splay angle to construct a phylomorphospace, and to perform a comparative disparity analysis considering ecomorphologically relevant characters related to swimming and diving. Coots resulted to be significantly disparate from other Rallidae showing many traits of specialized foot-propelled divers, but only noticeable when compared with other rallids, as the degree of development of these traits is markedly less than in loons, grebes, or cormorants. This may correspond to a stabilizing selection of characteristics associated with a generalist morphology in Fulica. Studying adaptation in generalist taxa broadens our understanding of ecomorphologically significant features, thereby enabling us to generalize their evolutionary patterns.

Exploring the Effects of Se Basicity on a Te···Se Interaction Supported by a Rigid Indazolium Backbone.

With an interest in chalcogen bonding, we use a rigid indazolium backbone to install a formally zero-valent Se center next to a divalent Te center, allowing us to investigate the effects of oxidation of the Se center on the observed Te···Se interaction. Through spectroscopic and computational comparison of the Se(0) species with its Se(II) counterpart and their monochalcogen analogues, we experimentally and computationally investigate the effect of modulating Se basicity on the resulting Te···Se interaction. Comparison with well-studied naphthalene and acenaphthene variants indicates that the increased basicity of the Se(0) center allows for a comparably strong Te···Se interaction despite longer peri distances and a larger splay angle. Finally, our study illuminates the potential non-innocence of cationic organic substituents in chalcogen-bonding catalysis of the transfer hydrogenation of quinolines.

Image-based assessment of aortoiliac aneurysm anatomical characteristics in patients from the global iliac branch study

ObjectiveEndovascular repair is the preferred treatment for aortoiliac aneurysm, with preservation of at least one internal iliac artery recommended. This study aimed to assess pre-endovascular repair anatomical characteristics of aortoiliac aneurysm in patients from the Global Iliac Branch Study (GIBS, NCT05607277) to enhance selection criteria for iliac branch devices (IBD) and improve long-term outcomes.MethodsPre-treatment CT scans of 297 GIBS patients undergoing endovascular aneurysm repair were analyzed. Measurements included total iliac artery length, common iliac artery length, tortuosity index, common iliac artery splay angle, internal iliac artery stenosis, calcification score, and diameters in the device's landing zone. Statistical tests assessed differences in anatomical measurements and IBD-mediated internal iliac artery preservation.ResultsLeft total iliac artery length was shorter than right (6.7 mm, P = .0019); right common iliac artery less tortuous (P = .0145). Males exhibited greater tortuosity in the left total iliac artery (P = .0475) and larger diameter in left internal iliac artery's landing zone (P = .0453). Preservation was more common on right (158 unilateral, 34 bilateral) than left (105 unilateral, 34 bilateral). There were 192 right-sided and 139 left-sided IBDs, with 318 IBDs in males and 13 in females.ConclusionThis study provides comprehensive pre-treatment iliac anatomy analysis in patients undergoing endovascular repair with IBDs, highlighting differences between sides and sexes. These findings could refine patient selection for IBD placement, potentially enhancing outcomes in aortoiliac aneurysm treatment. However, the limited number of females in the study underscores the need for further research to generalize findings across genders.

Peak effects induced by particle irradiations in 2H-NbSe2

Various peak effects in 2H-NbSe2 single crystals induced by particle irradiations were studied. 3 MeV proton irradiation magnified the peak effect induced by order–disorder (O-DO) transition of vortices, where the peak field shifts from high fields to low fields with increasing irradiation dose. For the peak effect in NbSe with splayed columnar defects (CDs), as the splayed angle increases, peak field gradually shifts from high fields to low fields. Numerical calculations have been conducted to investigate the mechanism of the peak effect. The calculated results exhibit excellent agreement with experimental observations. Analyses of field dependence of J reveal the formation of non-uniform J flow with increasing splayed angle, which plays a crucial role in inducing the self-field peak effect in superconductors with splayed CDs. In samples with symmetric splayed CDs with respect to the c-axis generated by 800 MeV Xe and 320 MeV Au ions, coexistence of O-DO transition-induced peak effect and self-field peak effect was observed. In the case of 320 MeV Au irradiated samples, when the splay angle is small, the two peak effects transform into a broad peak, which has similarity to the anomalous peak effect observed in iron-based superconductors. Interestingly, the broad anomalous peak effect is strongly suppressed when the external magnetic field is applied parallel to one of splayed CDs.

Honeybees Use Multiple Invariants to Control Their Altitude.

How do bees perceive altitude changes so as to produce safe displacements within their environment? It has been proved that humans use invariants, but this concept remains little-known within the entomology community. The use of a single invariant, the optical speed rate of change, has been extensively demonstrated in bees in a ground-following task. Recently, it has been demonstrated that another invariant, the splay angle rate of change, could also be used by bees to adjust their altitude. This study aims to understand how bees use these invariants when they are available simultaneously. This issue has been addressed using an experimental setup providing discordant information to bees. We have shown that when the two invariants were available, bees performed ground-following tasks relying primarily on optical speed rate of change. Conversely, when optical speed rate of change was less easily accessible, splay angle rate of change was prioritized, unless the bees perceive danger. Taken together, these results illustrate how the joint use of several invariants allows bees to produce adaptive behaviors.

An experimental setup for decoupling optical invariants in honeybees’ altitude control

Bees outperform pilots in navigational tasks, despite having 100,000 times fewer neurons. It is commonly accepted in the literature that optic flow is a key parameter used by flying insects to control their altitude. The ambition of the present work was to design an innovative experimental setup that would make it possible to determine whether bees could rely simultaneously on several optical invariants, as pilots do. We designed a flight tunnel to enable manipulation of an optical invariant, the Splay Angle Rate of Change (SARC) and the restriction of the Optical Speed Rate of Change (OSRC) in the optic flow. It allows us to determine if bees use the SARC to control their altitude and to identify the integration process combining these two optical invariants. Access to the OSRC can be restricted by using different textures. The SARC can be biased thanks to motorized rods. This device allows to record bees’ trajectories in different visual configurations, including impoverished conditions and conditions containing contradictory information. The comparative analysis of the recorded trajectories provides first time evidence of SARC use in a ground-following task by a non–human animal. This new tunnel allows a precise experimental control of the visual environment in ecological experimental conditions. Therefore, it could pave the way for a new type of ecologically based studies examining the simultaneous use of several information sources for navigation by flying insects.

Peak Effects in 2H-NbSe2 Single Crystals Introduced with Artificial Defects by Particle Irradiation

Effects of splayed columnar defects in NbSe2 single crystals introduced by 800 MeV Xe and 320 MeV Au irradiations were studied. Peak effects have been observed for both samples. For 320 MeV Au irradiated samples, the peak field is found to increase with increasing the splay angle, while in samples irradiated by 800 MeV Xe the peak field shows an opposite dependence. The temperature dependence of the peak field for these two samples are also different. Based on the analysis of pinning force density, this different temperature dependence of the peak field may originate from the different pinning mechanisms.

Experimental analysis of additively manufactured air-cooled splayed end-windings

Modern electrical machines for applications including aerospace and automotive need to meet an ever-increasing demand for power density. AC machines are required to operate at high fundamental frequencies, which produce high losses due to the AC skin and proximity effect mechanisms. Machines are limited in power density by the maximum operating temperature of the winding electrical insulation and therefore the ability of a machine to dissipate internally generated losses in the winding and core regions. Additive manufacturing has potential to significantly improve the ability of machines to dissipate heat, whilst reducing AC losses and improving package space by offering the designer unparalleled geometric freedom both in the active length and end-winding. In conjunction, electrical insulation with higher temperature ratings may be used. By forming the endwinding as a heat sink structure, the effective heat transfer coefficient can be substantialy increased, providing new opportunities in end-winding cooling. In this paper, the effect of splayed end-windings are evaluated for their use as a heat sink. The windings are tested experimentally with respect to their splay angle, and air velocity. The paper contains the results of the experimental testing for the convective heat transfer coefficients for electrically uninsulated additively manufactured components.

Ophthalmic Anthropometry Versus Spectacle Frame Measurements

Purpose: Refractive errors among children are on the rise and more children are wearing spectacle correction. Selecting an appropriate frame that conforms to the child's developing facial features is vital for comfortable spectacle wear. This study aimed to analyze the relationship between the facial and frame measurements in spectacle-wearing children in southern India. Materials and Methods: This observational study included spectacle-wearing children aged 5–17 years. Participants were enrolled from the Paediatric Outpatient Department of a tertiary care hospital and across various schools in southern India. The facial and frame measurements such as pupillary distance, crest height (CH), bridge projection, apical radius, distance between rims at 10 mm and 15 mm, frontal angle (FA), splay angle, front to bend, head width, temple width (TW), angle of side and downward angle of drop were measured using Rees Fairbanks facial gauge, head and TW caliper and Association of British dispensing opticians frame rule. Results: Hundred and four children participated in the study. Statistically significant differences (P &lt; 0.01, Wilcoxon signed-rank test) were observed between all facial and frame measurements such as CH, splay and FAs. Bland–Altman plots indicated large mean differences and wide limits of agreement between facial and frame measurements. Conclusion: Our study shows a large discrepancy between children's facial measurements and corresponding spectacle frame measurements. Many children were wearing reduced version of adult frames. This study highlights the need for dispensing age-appropriate spectacle frames for children. This may have implications for improved spectacle uptake and compliance.

Balloon-Augmented Leaflet Modification With Bioprosthetic or Native Aortic Scallop Intentional Laceration to Prevent Iatrogenic Coronary Artery Obstruction and Laceration of the Anterior Mitral Leaflet to Prevent Outflow Obstruction: Benchtop Validation and First In-Man Experience.

Bioprosthetic or native aortic scallop intentional laceration to prevent iatrogenic coronary artery obstruction (BASILICA) and laceration of the anterior mitral leaflet to prevent outflow obstruction (LAMPOON) reduce the risk of coronary and left ventricular outflow obstruction obstruction during transcatheter aortic valve replacement and transcatheter mitral valve replacement. Despite successful laceration, BASILICA or LAMPOON may fail to prevent obstruction caused by inadequate leaflet splay in patients having challenging anatomy such as very small valve-to-coronary distance, diffusely calcified, rigid leaflets, or undergoing transcatheter aortic valve replacement inside existing transcatheter aortic valve replacement. We describe a novel technique of balloon-augmented (BA) leaflet laceration to enhance leaflet splay. We measured the incremental leaflet splay from BA-BASILICA in vitro. From November 2019 to March 2021, 16 patients underwent BA-BASILICA and 4 BA-LAMPOON at 3 centers. BA-BASILICA increased benchtop leaflet tip splay 17%, maximum splay angle 30%, and splay area 23%, resulting in a more rounded apex and larger effective area. Sixteen patients at risk for inadequate BASILICA leaflet splay, including 4 transcatheter aortic valve replacement inside existing transcatheter aortic valve replacement, underwent BA-BASILICA. All had successful leaflet laceration. One had coronary obstruction requiring immediate orthotopic stenting. Two underwent elective orthotopic coronary stenting through the transcatheter valve cells for leaflet prolapse without coronary ischemia. There were no deaths during the procedure or at 30 days. Four patients at risk for inadequate anterior mitral leaflet splay underwent BA-LAMPOON. All had successful target leaflet laceration without left ventricular outflow obstruction obstruction or procedural death. One died within 30 days. BA leaflet laceration enhances leaflet splay in vitro and may allow transcatheter aortic valve replacement and transcatheter mitral valve replacement in patients otherwise ineligible for traditional BASILICA or LAMPOON due to challenging anatomy. Graphic Abstract: A graphic abstract is available for this article.

Peak Effects in 2H-NbSe2 Single Crystals Induced by Particle Irradiations

Effects of three kinds of columnar defects in NbSe2 single crystals introduced by 320 MeV Au irradiation with a dose equivalent matching field B Φ up to 4 T were studied. Through the magnetization measurement using a SQUID magnetometer, two pronounced peak effects in the external field dependence of critical current density (J c) were observed in crystals introduced with splayed and tilted columnar defects. In crystals with splayed columnar defects, J c at the peak field reaches the maximum for splay angle θ CD = ±10°, which is a little different from that found in YBa2Cu3O7 and iron-based superconductors, where optimal θ CD is equal to ±5°.

CORRELATION BETWEEN WEIGHT OF SPECTACLE AND THE CONTACT AREA OF NOSE PADS WITH RESPECT TO STANDARD ALIGNMENT

Aim: To understand the co-relation between the weight of spectacle and the contact area of nose pads with respect to standard alignment. Study Design: A cross-sectional study. Method: Parameters such as weight of spectacle, frontal angle of nose and nose pads, splay angle of nose and nose pads and pantoscopic angle, area of nose pads and contact area of nose pads were measured using simple tools such as portable weighing machine and a handmade gauge similar to Fairbanks facial gauge and the correlation between all the parameters was found out. Results: Out of total 75 frames, 42 frames (56%) had no change in contact area with the corresponding area of nose pads with respect to the parameters including weight of spectacle frontal angle, splay angle and pantoscopic angle in standard alignment of spectacle, while other 33 frames (44%) had a noticeable change in the contact area of nose pads with respect to the corresponding parameters. Conclusion: Difference of 50mm2 of area between contact area and area of nose pads is ac-ceptable with current trend of frames. Current trend of light weight frames and lenses has given ease to alignment as even misalignment does not result into marks. Contact area corresponding with the area of nose pad play a significant role in distribution of spectacle weight on nose. Mismatch between contact area and area of nose pads will result into skin marks. Ideally, a wearer is happy when standard alignment is achieved with respect to facial measurements.

Critical current density in anisotropic superconductors containing columnar defects

In order to reveal the influence of the tilt angle of columnar defects on angular dependence of critical current density the Monte Carlo simulation of vortex system in three-dimensional layered high-temperature superconductor (HTSC) was performed. For simulations, the three-dimensional model of layered HTSC generalized for the case of tilted magnetic field was used. The angular dependencies of the critical current were calculated at different splay angle of columnar defects and different anisotropy of HTSC. It was shown that simulation results correspond qualitatively to the experimental results for REBCO coated conductors.

Field-driven transition in the Ba1−xKxFe2As2 superconductor with splayed columnar defects

Through 2.6 GeV U irradiations, we have induced bimodal splayed columnar defects in Ba$_{1-x}$K$_x$Fe$_2$As$_2$ single crystals with splay angles, $\pm 5 ^\circ$, $\pm 10 ^\circ$, $\pm 15 ^\circ$, and $\pm 20 ^\circ$. Critical current densities through magnetization measurements were carefully evaluated, where a splay angle of $\pm 5 ^\circ$ brought about the highest $J_\mathrm{c}$. Mageto-optical images close to $T_\mathrm{c}$ indicates highly anisotropic discontinuity lines in the remnant state, and with anisotropy increasing with greater splay angles. Moreover, amongst those with splayed columnar defects, anomalous non-monotonic field dependences of $J_\mathrm{c}$ and $S$ with an extrema at some fraction of the matching field are observed. We discuss that such $J_\mathrm{c}$ enhancement arises from a field-driven coupling transition in which intervortex interactions reorganize the vortex structure to be accommodated into columnar defects, thereby increasing pinning at higher fields.

Ischemic-reperfusion of unilateral external iliac artery in rat: A new model for vasculitic femoral neuropathy

Clinically, ischemic environment during gynecological surgery at lithotomy position is most common causative factor for the development of vasculitic femoral neuropathy (VFN). The present study was designed to induce the clinically relevant rat model of VFN by ischemic-reperfusion (I/R) injury of unilateral external iliac artery (uEIA). The VFN was induced by 3, 4 and 5h occlusion of uEIA followed by reperfusion. The I/R of uEIA induced VFN was evaluated by (i) behavioral parameters i.e., hind limb temperature; weight bearing capacity; (ii) kinematic analysis i.e., paw posture, splay angle, static sciatic index (SSI), and ankle-angle tests; (iii) evaluation of pain perception i.e., plantar and pin prick; (iv) serum biochemical estimation i.e., nitrate, lipid peroxidation, TNF-α and calcium level; (v) evaluation of motor and sensory nerve conduction velocity; and (vi) measurement of nerve fiber density. The 4 and 5h occlusion of uEIA has produced the potential changes in behavioral, functional, electrophysiological, biochemical and histopathological assessment. The 5h occlusion of uEIA has shown to produce the mortality. Whereas, 3h occlusion does not produce the significant changes in the development of VFN. The 4h ischemic occlusion of uEIA has shown potential rat model of VFN due to its close mimicking capacity of VFN in human. Therefore, it can be useful to explore the newer anti-neuralgic medicine and with their pharmacodynamic action in the field of various neurovascular disorders.

Flux pinning in Ba[formula omitted]KxFe2As2 superconductor with splayed columnar defects

It has been theoretically proposed that the enhancement of the critical current density (Jc) through dispersing the angle of columnar defects should be greater than that of parallel columnar defects. Yet, the complication caused by decrease in pinning owing to vortex-field misalignment upon tilting of columnar defect makes it a crucial task to determine the optimal splay angle in order to fully take advantage of enhanced pinning among splayed systems. Using Ba0.6K0.4Fe2As2 as a target material, we probe the effects of various splay angles on Jc and determine that the ‘optimal-angle’ lies within the small angle range (0--10∘).

Membrane-mediated aggregation of anisotropically curved nanoparticles.

Using systematic numerical simulations, we study the self-assembly of elongated curved nanoparticles on lipid vesicles. Our simulations are based on molecular dynamics of a coarse-grained implicit-solvent model of self-assembled lipid membranes with a Langevin thermostat. Here we consider only the case wherein the nanoparticle-nanoparticle interaction is repulsive, only the concave surface of the nanoparticle interacts attractively with the lipid head groups and only the outer surface of the vesicle is exposed to the nanoparticles. Upon their adhesion on the vesicle, the curved nanoparticles generate local curvature on the membrane. The resulting nanoparticle-generated membrane curvature leads in turn to nanoparticle self-assembly into two main types of aggregates corresponding to chain aggregates at low adhesion strengths and aster aggregates at high adhesion strength. The chain-like aggregates are due to the fact that at low values of adhesion strength, the nanoparticles prefer to lie parallel to each other. As the adhesion strength is increased, a splay angle between the nanoparticles is induced with a magnitude that increases with increasing adhesion strength. The origin of the splay angles between the nanoparticles is shown to be saddle-like membrane deformations induced by a tilt of the lipids around the nanoparticles. This phenomenon of membrane mediated self-assembly of anisotropically curved nanoparticles is explored for systems with varying nanoparticle number densities, adhesion strength, and nanoparticle intrinsic curvature.

Aging and Muscle Activity Patterns during Cycling

Objective: The purpose of this study was to evaluate the muscle activation patterns of lower limb muscles during 90-second trials at randomly assigned workloads (0 and 100 W) with a constant cadence (60 rpm) in young and older healthy adults. Methods: Twelve healthy, male, novice cyclists classified by age into two groups of young and older. Electromyographic (EMG) data were recorded from rectus femoris (RF), biceps femoris (BF), tibialis anterior (TA), and gastrocnemius medialis (GT). Joints kinematics was also recorded simultaneously. A performance index (PI) was developed to evaluate the characteristics of muscle recruitment between workloads. Results: EMG duration and peak magnitude increased significantly with increased workload in RF and BF in both groups. PI Values indicated that BF and RF had similar increases with increased workload for both groups, while younger groups had higher activation of TA (52% v/s 28%) and older group had higher activation of GT (17% v/s 1%). Both groups exhibited significant increases (p<0.05) in the co-activation of upper leg agonist and antagonist muscles as workload increased. Duration of co-activation between the upper and lower leg muscles of the young group significantly increased (p<0.05) with workload. The ROM of the knee splay angle in the older group showed a significant difference (p<0.05) compared to the young. Conclusion: The alteration in limb muscle activation and coordination is not parallel between young and older adults. Older adults appear to use a different strategy in recruiting more muscle fibre to generate the same work. These findings are an indication that the threshold for muscle adaptation may differ between young and old adults. It is recommended that rehabilitation professionals consider these differences and recognize that the stimulus required to promote positive change in older skeletal muscles might be different from what may require for young adults.

Acenaphtho[5,6-cd]-1,2-dichalcogenoles and their platinum complexes

A related series of bis(phosphine) platinum complexes 1–5 and 6–8 bearing dichalcogenate acenaphthylene ligands have been synthesised. The chalcogen–chalcogen bonds in the parent acenaphtho[5,6-cd]-1,2-dichalcogenoles (AcenapylE2; L1 E=S, L2 E=Se; Acenapyl=acenaphthylene-5,6-diyl) were reduced with two equivalents of lithium triethylborohydride to form the dilithio-species. Metathetical addition of the lithium dichalcogenate species to a suspension of the appropriate cis-dichlorobis(phosphine)platinum in THF resulted in the formation of platinum(II) complexes [Pt(5,6-AcenapylE2)(PR3)2] (1 E=S, R3=Ph3; 2 E=S, R3=Ph2Me; 3 E=S, R3=PhMe2; 4 E=S, R3=Me3; 6 E=Se, R3=Ph3; 7 E=Se, R3=Ph2Me; 8 E=Se, R3=PhMe2). The dilithio-species of L1 and L2 were also reacted with (1,5-cyclooctadiene)platinum(II) dichloride. This reaction was successful with L1 resulting in the formation of platinum complex [Pt(5,6-AcenapylS2)(COD)] (5). Complexes 1–3 and 5–8 have been fully characterised, principally by multinuclear magnetic resonance spectroscopy, IR and MS. Secondary isotopomer effects create complex satellite systems observed in both the 31P{1H} NMR and 77Se NMR spectra of selenium complexes 6–8. X-ray structures were determined for L1, 1, 3 and 6 and analysed, where appropriate, by measuring the peri-distance, splay angle magnitude, peri-atom displacement, central naphthalene ring torsions and the geometry around the platinum centre. Platinum was found to adopt a distorted square-planar geometry in all three complexes. Complex 1 was found to have the greatest molecular distortion of all three complexes, showing that changing the phosphine group and also the chalcogen has a noticeable effect. Comparisons were made between 6 and our previously reported [Pt(NapSe2)(PPh3)2] and [Pt(AcenapSe2)(PPh3)2] complexes; the level of distortion was found to decrease as the backbone is altered from naphthalene to acenaphthylene.