Longitudinal Extensions Research Articles

Synthesis, Characterization, and Photochemistry of a Ga2L3 Coordination Cage with Dithienylethene-Catecholate Ligands.

Two new photoswitchable dithienylethene (DTE)-catechol ligands, specifically designed for group 13 metal coordination, were synthesized via Suzuki coupling reactions from a dichloro-DTE building block, each with varying longitudinal extensions. The shorter DTE-catechol ligand did not efficiently assemble with Ga3+ metal ions; however, elongation with a phenylene-amide spacer group enabled the successful formation of a novel triply DTE-functionalized coordination [Ga2L3]6- cage. This cage represents a unique example of integrating DTE photoswitches with main group metals in a supramolecular coordination framework. The [Ga2L3]6- cage was thoroughly characterized by NMR spectroscopy, including DOSY hydrodynamic volumetric analyses, high-resolution mass spectrometry, computational DFT, and photochemical analyses. The DFT studies highlighted the structural integrity and dynamic interplay within the helicate and mesocate isomeric forms of the [Ga2L3]6- cage upon photoswitching. While the free ligands exhibited all-photonic reversible switching at up to mM concentrations upon alternating irradiation at 365 and >495 nm, the [Ga2L3]6- cage demonstrated these capabilities under dilute μM conditions, albeit with lower efficiency and fatigue resistance. This behavior highlights the intricate relationship between rigid coordination with main group metals and the flexibility of the photoswitchable DTE ligands within the [Ga2L3]6- cage.

Intrahepatic cholangiocarcinoma with extensive intraductal extension of high-grade biliary intraepithelial neoplasia: a case report

BackgroundIntrahepatic cholangiocarcinoma (ICC) is frequently associated with precursor lesions, and biliary intraepithelial neoplasia (BilIN) may play a significant role in the development of ICC. However, the exact sequence and progression of these lesions remain to be elucidated. We report a rare case of ICC that exhibited extensive longitudinal intraductal extension of high-grade BilIN in the posterior bile ducts and involved the hepatic hilum and the peripheral hepatic parenchyma.Case presentationA 70-year-old female presented with anorexia. Computed tomography (CT) revealed a 15 mm enhancing intrahepatic tumor extending to the right intrahepatic secondary confluence. This was associated with a 7 mm diameter cystic dilatation of the segment 6 bile duct (B6). Endoscopic retrograde cholangiopancreatography (ERCP) revealed stenosis at the bifurcation of the posterior bile duct branch. Bile cytology confirmed the diagnosis of adenocarcinoma cells. Therefore, the patient was diagnosed with an ICC involving the right glissonean pedicle and underwent a right hepatectomy and lymph node dissection. Histologic examination revealed the tumor consisted of moderately differentiated adenocarcinoma. In connection with this lesion, diffuse intraductal atypical epithelial cells, which were diagnosed as high-grade BilIN, was observed not only in the dilated B6 but in the entire posterior bile ducts, which measured approximately 120 mm in diameter. Furthermore, two distinct foci of adenocarcinomas were identified in the peripheral hepatic parenchyma. A lymph node metastasis was also present. The pathological diagnosis was ICC pT4N1M0 stage IVA. The patient underwent adjuvant chemotherapy and has shown no recurrence 5 years after surgery. Imaging modalities were unable to accurately assess the extent of the intraductal neoplastic lesions due to their low papillary or sessile intraductal tubular growth. No risk factors for BilIN development, which has the potential to predispose to cholangiocarcinoma, were identified in the present case.ConclusionsWe present a case of ICC involving the right hepatic hilum, accompanied by extensive longitudinal extensions of high-grade BilIN and multifocal microscopic invasions in peripheral hepatic parenchyma. Notably, the intraductal lesions involved the entire posterior intrahepatic bile ducts. The presence of biliary neoplasia with extensive intraductal extension, in conjunction with ICC, should be considered as a variant of BilIN.

The Small Area Estimation of Economic Security: A Proposal

The objective of this work is to propose a small area estimation strategy for an economic security indicator. In the last decade the interest for the measurement of economic security or insecurity has grown constantly, especially since the financial crisis of 2008 and the pandemic period. In this work, economic security is measures through a longitudinal indicator that compares levels of equivalized household income over time. To solve a small area estimation problem, due to possible sample sizes too low in some areas, a small area estimation strategy is suggested to obtain reliable estimates of the indicator of interest. We consider small area models specified at area level. Besides the basic Fay-Herriot area-level model, we propose to consider some longitudinal extensions, including time-specific random effects following an AR(1) process or an MA(1) process. A simulation study based on EU-SILC data shows that all the small area models considered provide a significant efficiency gain with respect to the Horvitz-Thompson estimator, especially the small area model with MA(1) specification for random effects.

Assessing the contributions of modifiable risk factors to serious falls and fragility fractures among older persons living with HIV.

Although 50 years represents middle age among uninfected individuals, studies have shown that persons living with HIV (PWH) begin to demonstrate elevated risk for serious falls and fragility fractures in the sixth decade; the proportions of these outcomes attributable to modifiable factors are unknown. We analyzed 21,041 older PWH on antiretroviral therapy (ART) from the Veterans Aging Cohort Study from 01/01/2010 through 09/30/2015. Serious falls were identified by Ecodes and a machine-learning algorithm applied to radiology reports. Fragility fractures (hip, vertebral, and upper arm) were identified using ICD9 codes. Predictors for both models included a serious fall within the past 12 months, body mass index, physiologic frailty (VACS Index 2.0), illicit substance and alcohol use disorders, and measures of multimorbidity and polypharmacy. We separately fit multivariable logistic models to each outcome using generalized estimating equations. From these models, the longitudinal extensions of average attributable fraction (LE-AAF) for modifiable risk factors were estimated. Key risk factors for both outcomes included physiologic frailty (VACS Index 2.0) (serious falls [15%; 95% CI 14%-15%]; fractures [13%; 95% CI 12%-14%]), a serious fall in the past year (serious falls [7%; 95% CI 7%-7%]; fractures [5%; 95% CI 4%-5%]), polypharmacy (serious falls [5%; 95% CI 4%-5%]; fractures [5%; 95% CI 4%-5%]), an opioid prescription in the past month (serious falls [7%; 95% CI 6%-7%]; fractures [9%; 95% CI 8%-9%]), and diagnosis of alcohol use disorder (serious falls [4%; 95% CI 4%-5%]; fractures [8%; 95% CI 7%-8%]). This study confirms the contributions of risk factors important in the general population to both serious falls and fragility fractures among older PWH. Successful prevention programs for these outcomes should build on existing prevention efforts while including risk factors specific to PWH.

Where Is Region 1 Field‐Aligned Current Generated?

AbstractWe investigate generation regions of the Region 1 field‐aligned currents (FACs) by using global magnetohydrodynamics (MHD) simulation for steady and purely southward interplanetary magnetic field (IMF). Unlike conventional means, we consider Alfvén traveling time and background motion of plasma. We trace “packets,” which are supposed to carry the perturbations associated with FACs, backward in time from the ionosphere. The following criteria are used to identify generation regions. (a) Conversion between field‐aligned and field‐perpendicular currents takes place (as required from current continuity). (b) Plasma performs negative work against the magnetic tension force (as required from energy conservation). (c) Rate of change in FACs is nonzero (as required from Ampère's and Faraday's laws). Flank (low‐latitude) magnetopause is identified to be a major generator region, in which solar wind‐originated plasma pulls the newly reconnected magnetic field lines. Magnetosphere‐originated plasma, which is indirectly pulled by the solar wind‐originated plasma, also participates in the generation. The involvement of the reconnection can explain the general dependence on the southward IMF. The generation of Region 1 FACs is associated with field‐aligned gradient of space charge ∇||(∇⋅E), where E is the electric field, but the contribution from the term (∇2E)|| is also significant because of curved magnetic field lines. The flank generator can reasonably explain the latitudinal and the longitudinal extensions of the Region 1 FACs because of the finite travel time of the Alfvén waves under convective motion. The generation region is located apart from the instantaneous magnetic field lines extending from the ionosphere.

Sediment Transport Dynamism in the Confluence Area of Two Rivers Transporting Mainly Suspended Sediment Based on Sentinel-2 Satellite Images

Downstream of the confluence of rivers, complex hydrological and morphological processes control the flow and sediment transport. This study aimed to analyze the spatio-temporal dynamics of suspended sediment in the confluence area of the Tisza and its main tributary Maros River using Sentinel-2 images and to reveal the correlation between the hydrological parameters and the mixing process through a relatively long period (2015–2021). The surficial suspended sediment dynamism was analyzed by applying K-means unsupervised classification algorithm on 143 images. The percentages of the Tisza (TW) and Maros (MW) waters and their mixture (MIX) were calculated and compared with the hydrological parameters in both rivers. The main results revealed that the areal, lateral, and longitudinal extensions of TW and MIX have a better correlation with the hydrological parameters than the MW. The Pearson correlation matrix revealed that the discharge ratio between the rivers controls the mixing process significantly. Altogether, 11 mixing patterns were identified in the confluence area throughout the studied period. The TW usually dominates the confluence in November and January, MW in June and July, and MIX in August and September. Predictive equations for the areal distribution of the three classes were derived to support future water sampling in the confluence area.

Clustering Indoor Positioning Data Using E-DBSCAN

Indoor positioning data reflects human mobility in indoor spaces. Revealing patterns of indoor trajectories may help us understand human indoor mobility. Clustering methods, which are based on the measurement of similarity between trajectories, are important tools for identifying those patterns. However, due to the specific characteristics of indoor trajectory data, it is difficult for clustering methods to measure the similarity between trajectories. These characteristics are manifested in two aspects. The first is that the nodes of trajectories may have clear semantic attributes; for example, in a shopping mall, the node of a trajectory may contain information such as the store type and visit duration time, which may imply a customer’s interest in certain brands. The semantic information can only be obtained when the position precision is sufficiently high so that the relationship between the customer and the store can be determined, which is difficult to realize for outdoor positioning, either using GPS or mobile base station, due to the relatively large positioning error. If the tendencies of customers are to be considered, the similarity of geometrical morphology does not reflect the real similarity between trajectories. The second characteristic is the complex spatial shapes of indoor trajectory caused by indoor environments, which include elements such as closed spaces, multiple obstacles and longitudinal extensions. To deal with these challenges caused by indoor trajectories, in this article we proposed a new method called E-DBSCAN, which extended DBSCAN to trajectory clustering of indoor positioning data. First, the indoor location data were transformed into a sequence of residence points with rich semantic information, such as the type of store customer visited, stay time and spatial location of store. Second, a Weighted Edit Distance algorithm was proposed to measure the similarity of the trajectories. Then, an experiment was conducted to verify the correctness of E-DBSCAN using five days of positioning data in a shopping mall, and five shopping behavior patterns were identified and potential explanations were proposed. In addition, a comparison was conducted among E-DBSCAN, the k-means and DBSCAN algorithms. The experimental results showed that the proposed method can discover customers’ behavioral pattern in indoor environments effectively.

Is Right or Left Hepatic Resection Better for Perihilar Cholangiocarcinoma? A Cadaveric Study on the Length of the Right and Left Hepatic Ducts

Introduction: The optimal surgical procedure for perihilar cholangiocarcinoma is based on tumor location and the longitudinal and horizontal extensions. Right-sided hepatectomy is often used because it appears to be oncologically advantageous assuming that, in addition to possible arterial involvement, the left hepatic duct is longer than the right and a negative ductal margin is expected. However, few studies addressed the length of the duct in normal livers. The aim of this study is to examine the lengths of the right and left hepatic ducts to guide surgical strategy for perihilar cholangiocarcinoma.

Dolphinfish movements in the Eastern Pacific Ocean of Mexico using conventional and electronic tags

BackgroundThe dolphinfish, Coryphaena hippurus, is a fast-swimming, predatory fish exhibiting relatively fast growth and early maturation among marine teleosts. It is an important, potentially renewable resource throughout its global subtropical-to-tropical range. Understanding the ecology of this wide-ranging fish is critical to proper fisheries management, but studies have historically depended heavily upon aggregated catch data reported by fisheries. This study uses tagging data to explore finer scale dolphinfish movements in two subregions of the Eastern Pacific Ocean (EPO)—the west coasts of Baja California Peninsula (WBC) and Oaxaca (OAX), Mexico.ResultsAdult dolphinfish (fork length 66–129 cm) were tagged with conventional (n = 132 tags) and electronic tags (n = 30 tags, miniPAT) between 2010 and 2014. Recapture rate of conventional tags was 4.5% with a maximum days of liberty of 141 days (mean = 56 d); 20 electronic tags reported but all did so prior to programmed release dates, with days at liberty ranging from 4 to 62 (mean = 24 d). Fish remained within the region they were tagged except for six fish tagged in WBC and one in OAX. Latitudinal (WBC) and longitudinal (OAX) extensions of observed fish movements (determined via a novel analytical approach) increased with days at liberty. Despite occasional deep dives (max 262 m), fish remained surface oriented with short excursions below the isothermal layer but larger OAX fish (fork length [103 cm, 120 cm]) inhabiting warmer waters (sea surface temperatures (SST) > ~ 26 °C) spent more time below the isothermal layer than smaller fish (fork length [90 cm, 112 cm]) inhabiting colder WBC surface waters (SST > ~ 22 °C).ConclusionsThis study reveals movements of dolphinfish that infer regional differences in thermal habitat utilization and displacement over time. This inference evokes questions important to fisheries management regarding the three-dimensional extent of the dolphinfish’s realized thermal niche, its population structure, and the spatiotemporal connectivity of its habitats within the multinational EPO. With improved tag retention, longer deployments should capture increasing displacements along observed axes (N/S vs. E/W); the orientation of seasonal displacement axes suggest longer-distance movements would provide opportunities for reproductive mixing via trans-national migrations.

Evaluation of SpyGlass DS for longitudinal extensions of bile duct cancer

Evaluation of SpyGlass DS for longitudinal extensions of bile duct cancer

Strain stiffening of peripheral nerves subjected to longitudinal extensions in vitro

The mechanical response of peripheral nerves is crucial to understand their physiological and pathological conditions. However, their response to external mechanical solicitations is still partially unclear, since peripheral nerves could behave in a quite complex way. In particular, nerves react to longitudinal strains increasing their stiffness to keep axons integrity and to preserve endoneural structures from overstretch. In this work, the strain stiffening of peripheral nerves was investigated in vitro through a recently introduced computational framework, which is able to theoretically reproduce the experimental behaviour of excised tibial and sciatic nerves. The evolution and the variation of the tangent modulus of tibial and sciatic nerve specimens were quantitatively investigated and compared to explore how stretched peripheral nerves change their instantaneous stiffness.

Clinical Outcome of Magnetically Controlled Growing Rod in Early-onset Scoliosis: A Systematic Review.

This was a systematic literature review. To evaluate the efficacy and safety of magnetically controlled growing rod (MCGR) in treating early-onset scoliosis. Preliminary studies reported the promising potential of MCGR in deformity correction and spine growth preservation with noninvasive distraction. This study was conducted on the basis of data from published literatures. A systematic search from multimedical database was conducted for studies of MCGR. Involved studies should provide at least one of the followings: deformity correction, spine growth, and complication. During treatment period, improvement or progression of scoliosis/kyphosis, annual T1-S1/T1-T12 extension, incidence of complication, and unplanned surgery were summarized and the correlations with term of follow-up were investigated. In total, 13 studies (n=249) were involved, with an average of 22.2-month follow-up. Scoliosis correction was well maintained, improving from 36.4 degrees at postinitial to 37.1 degrees at last follow-up (P=0.794). Kyphosis progressed from 28.8 degrees at postinitial to 34.4 degrees at last follow-up (P=0.024). Annual T1-S1 and T1-T12 longitudinal extensions were 8.7 and 4.7 mm/year, respectively. As follow-up went on, no significant decline was observed in annual extension of T1-S1 (P=0.4680) or T1-T12 (P=0.8053). The incidences of alignment-related, implant-related, and wound-related complication were 3.5%, 30.1%, and 6.9%, respectively. No significant correlation was observed between occurrence of complication and term of follow-up. The rate of receiving unplanned surgery was 24.3%. MCGR is efficient in the maintenance of coronal correction and preservation of spine growth, with loss of sagittal correction and a 24.3% unplanned revision rate.

The etiologies and prognosis associated with spinal cord infarction.

BackgroundThis study aims to investigate the etiology and prognosis of spinal cord infarction (SCI).MethodsOver a period of 16 years, we retrospectively analyzed 31 patients with SCI. Demographic features and symptom presentations were carefully documented. Etiology‐specific MRI features, such as the length and distribution of the lesions and owl’s eyes sign, were recorded and analyzed to determine their associations with the clinical signs/symptoms.ResultsIn total, seven patients had aortic or vertebral artery dissections. We divided the patients with SCI into two groups: those with or without vessel dissection. Among SCI patients, the onset age was younger, and the proportion of patients with long‐segment lesions and posterior pattern involvement on axial view was higher in the group with dissection than in the group without dissection (all P < 0.05). The lesions were frequently located in the upper cervical or lower thoracic‐lumbar regions, and the lengths of the lesions were associated with 1‐month outcomes, suggesting that artery dissection may contribute to the longitudinal and posterior extension of SCI. In contrast, among patients without dissection, the range of longitudinal extensions of in spans of vertebral bodies was broader (range, 1–8). A higher proportion of patients had focal pain adjacent to the lesion (P = 0.05) and a poorer 1‐month outcome (P = 0.04) in the long‐segment lesion group than in the short‐segment lesion group.ConclusionsA detailed history and the use of modern imaging tools may help clinicians search for vessel dissection and other etiologies, evaluate the spatial extension of lesions in SCI, and predict prognosis.

Composite Strips with U-Shaped CFRP Wrap Anchor Systems for Strengthening Reinforced Concrete Beams

The contribution of carbon fiber reinforced polymer (CFRP) wrap as an anchorage system of CFRP plates, used for flexural strengthening, is investigated. Eighteen concrete beams (100 × 150 × 1400 mm3) were cast and cured for 28 days before strengthening with both CFRP plates (1.2 × 50 mm2) and anchorage-used, U-shaped CFRP wraps. These were adhered on the top of the CFRP plates at different longitudinal and transverse extensions. The mechanical response of the concrete beams was examined under four-point loading including measurements of load versus deflection, bond stress versus slippage and strain in CFRP plates. Crack formation and failure modes were also monitored and characterized. End anchorage regimes, using 300-mm-long U-shaped segmented CFRP wraps, impart the best improvement to load capacity, rigidity, and toughness (up to 80, 57, and 40%, respectively) without harming tangibly ductility in terms of deflection at failure. Anchorage cases involving attaching continuous single or double layers of U-shaped CFRP wrap on the top of CFRP plates impart lower but tangible overall improvements in mechanical performance of CFRP-strengthened beams. A simple empirical model is developed to predict ultimate strain in CFRP plate based on present results before examining using available literature data. Moreover, the efficiency of the present technique is compared to that present in literature.

Shaking table tests on discrepant responses of shaft-tunnel junction in soft soil under transverse excitations

Due to the special configurations of the shaft-tunnel junction, discrepant responses of the shaft and the tunnel will arise when earthquakes strike. This paper presents shaking table tests addressing this discrepancy and its influence on the structures. The model system is designed to reproduce the relative stiffness and the relative mass of the prototype system. Two site-specific synthetic earthquake motions are adopted as seismic excitations along the transverse direction of the tunnel model. The discrepant responses are revealed by the shaft's and the tunnel's acceleration responses. The extent of discrepancy is quantified by correlation coefficients, and its influence on structural performance is evaluated. Consequently, the longitudinal circumferential-joint extensions and the transverse dynamic strains are raised at the shaft-tunnel junction. While the raised strains are relatively small, the longitudinal circumferential-joint extensions pose a threat to structural safety. A simplified model based on the solution for Euler-Bernoulli beam on Winkler foundations is put forward to establish the relation of circumferential-joint extensions and shaft-tunnel relative displacements. Validation of the proposed model is conducted by comparison of test results and analytical results.

Spatial characteristics of recurrent ionospheric storms at low latitudes during solar minimum

Low-latitude ionospheric disturbances with amplitudes of 20 TECU occurred during moderate recurrent magnetic storms were analyzed in time period from 2007 to 2008. The analysis of these so-called recurrent ionospheric storms (RISs) was based on global ionospheric maps of vertical total electron content derived from the ground based GPS network. It was found that positive RISs were developed predominantly in the noon and postnoon sector and they have very large latitudinal and longitudinal extensions of up to 70 and 160°, respectively. Negative RISs occur mainly in the evening sector and they have ∼1.5 time smaller latitudinal and longitudinal extensions. The different location and spatial scales can be explained by different origins of the ionospheric storms. The large-scale positive ionospheric storms are generated by the mechanism of prompt penetration electric field, operating on the dayside, and by equatorward neutral wind disturbance. The negative storms can be related to the mechanism of disturbance dynamo electric field, operating in the evening sector, and to the changing of the thermospheric neutral composition, operating on sunlight side.

Experimental study on merging behaviors of two identical buoyant diffusion flames under an unconfined ceiling with varying heights

This paper presents an experimental study on the flame merging behaviors of two identical square propane burners with the side length of 15 cm burning under an unconfined ceiling. The total heat release rate of the two burners, burner edge spacing and ceiling height above the burner were varied. The flame merging probability, both the longitudinal and transverse ceiling flame extensions respectively along and perpendicular to the line connecting the centers of the two burners were measured. Based on the dimensional analysis, a piecewise linear function for the flame merging probability was developed and the criteria of the beginning and fully merging of the ceiling flames were thus determined, which provides a guidance of the safety distance between combustibles in buildings. The flame length is defined as the half of the total ceiling flame length in this work. Due to the interaction of two burners, the longitudinal and transverse flame lengths are different. Experimental results showed that as the spacing increases, the longitudinal flame length increases while the transverse flame length decreases. Based on the energy distribution model developed for the vertical and ceiling flames, correlations for predicting the merging ceiling flame lengths in the two directions were respectively established as the functions of the total heat release rate, burner size and spacing, ceiling height and the free flame height of two burners with zero spacing. The proposed models for the ceiling flame lengths can help to better understand the fire ignition and spread probability and flame radiation properties.

Longitudinal Thin Structure of Equatorial Plasma Depletions Coincidently Observed by Swarm Constellation and all‐Sky Imager

AbstractThe lower pair satellites of Swarm mission, flying side‐by‐side and separated by 1.4° in longitude (about 150 km), usually observed equatorial plasma depletions (EPDs) showing quite different structures, and sometime even only one satellite observed EPD. In this study, we provided 6‐h continuous observations of EPDs on the night of 23–24 September 2014, from an all‐sky imager located at Fuke (geographic:19.5°N,109.1°E), south of China. From the airglow images the EPDs were found with longitudinal extensions of about 50 km and all tilted from northwest to southeast direction. We further checked the in situ electron density simultaneously measured by the Swarm lower pair satellites and found the differences of Swarm in situ electron densities explained well by the longitudinally thin structure of EPDs observed from the all‐sky imager. During later periods the bifurcation and merging were observed by the airglow images, and it was the first time to report both processes in the evolution of one EPD. The bifurcation was first observed at the higher‐latitude part, and then observed at lower latitudes of EPD. The subbranches generated through bifurcation showed even thinner longitudinal extension of about 20–30 km, and later the subbranches started to merge with each other, forming a really complicated mesh of depleted regions.

Spatial rectal dose/volume metrics predict patient-reported gastro-intestinal symptoms after radiotherapy for prostate cancer

Background: Gastro-intestinal (GI) toxicity after radiotherapy (RT) for prostate cancer reduces patient’s quality of life. In this study, we explored associations between spatial rectal dose/volume metrics and patient-reported GI symptoms after RT for localized prostate cancer, and compared these with those of dose–surface/volume histogram (DSH/DVH) metrics.Material and methods: Dose distributions and six GI symptoms (defecation urgency/emptying difficulties/fecal leakage, ≥Grade 2, median follow-up: 3.6 y) were extracted for 200 patients treated with image-guided RT in 2005–2007. Three hundred and nine metrics assessed from 2D rectal dose maps or DSHs/DVHs were subject to 50-times iterated five-fold cross-validated univariate and multivariate logistic regression analysis (UVA, MVA). Performance of the most frequently selected MVA models was evaluated by the area under the receiving–operating characteristics curve (AUC).Results: The AUC increased for dose-map compared to DSH/DVH-based models (mean SD: 0.64 ± 0.03 vs. 0.61 ± 0.01), and significant relations were found for six versus four symptoms. Defecation urgency and faecal leakage were explained by high doses at the central/upper and central areas, respectively; while emptying difficulties were explained by longitudinal extensions of intermediate doses.Conclusions: Predictability of patient-reported GI toxicity increased using spatial metrics compared to DSH/DVH metrics. Novel associations were particularly identified for emptying difficulties using both approaches in which intermediate doses were emphasized.

Variation in the growth and survival of the tropical vermetid gastropod Ceraesignum maximum is driven by size, habitat, and density

The vermetid Ceraesignum maximum is a sessile tube-dwelling snail with a wide geographic distribution that can strongly reduce the growth and survival of corals, alter coral morphology, and shift coral species composition. Thus, this species has the potential to drive dramatic changes in coral reef ecosystems; yet, very little basic demographic information exists for C. maximum; nor do we know factors that potentially contribute to variation in vital rates. This study estimated individual growth (change in shell aperture diameter) and survival of focal (tagged) vermetids (n = 297) over 646 days, to test hypotheses that growth and/or survival rates were size-dependent, density-dependent, and/or habitat-dependent. This study was conducted on 80 haphazardly selected patch reefs, split evenly among eight discrete sites. The design also incorporated an experimental density reduction (e.g. on half the study reefs at each site divers reduced the densities of vermetids). Vermetid growth rates decreased with body size, and the slope of this relationship was steeper for reefs with experimentally reduced densities. Vermetid growth decreased weakly with local biomass of vermetids (i.e. estimated biomass within a 20 cm radius of focal individuals) but did not vary with local substrate composition. Vermetid survival increased with body size and local biomass; the relationship with biomass was steeper for reefs where vermetid densities had been experimentally reduced. Survival was also greater on living coral Porites lobata (where coral growth covered longitudinal extensions of vermetid shells) relative to dead coral substrate (where vermetid shells extensions remained exposed). These data suggest little scope for regulation of vermetid population growth via direct density dependence in demographic rates. However, given that vermetids can kill corals, and vermetid survival probabilities appear to depend upon coral cover, it is predicted that vermetids may experience cyclical dynamics that are coupled to the dynamics of living coral.