Internal Ridges Research Articles

Beyond Endoscopes: Pilot Study of Surgical Instrument Lumen Inspection.

Objective: Borescope examinations of endoscope channels are commonly described in literature, but no studies on surgical instrument lumen inspection have been published recently. Inadequately processed surgical instruments have been implicated in patient infections. This study assessed the utility of borescopes for inspecting surgical instruments. Methods: The study team inspected and photographed sterilized, patient-ready arthroscopic shaver handpieces and suction tips using a tablet camera and borescopes to characterize internal anatomy, defects found in lumens, and the impact of recleaning on debris or residues. Results: Ten suctions and eight shavers were inspected. All suctions had internal ridges and suction holes that were perpendicular to the lumen. All shavers had visible ridges, elbows, and lever mechanisms inside lumens. Of the 18 instruments, 16 (88%) had internal features that appeared rough or jagged and 17 (94%) had visible debris or discoloration in the lumens. Recleaning efforts generally were effective for suctions, but multiple rounds of recleaning with enhanced steps were less effective for shavers, which were replaced. Researchers documented retained soil and brush bristles in several new shavers despite following manufacturer instructions for cleaning and found visible damage and discoloration within five uses. Discussion: This study demonstrated the value of borescope examinations for surgical instrument lumens. Visual inspections identified anatomical features that could influence cleaning effectiveness and detected residual soil, discoloration, and debris in most instruments. The findings suggested that manufacturer cleaning instructions were insufficient and additional cleaning was not always effective. In response, the site's multidisciplinary team strengthened risk assessment protocols and enhanced their cleaning practices.

A Comparative Study on the Stability Performance of the Suspen-Dome, Conventional Cable Dome, and Ridge-Beam Cable Dome

Stability calculation is the main objective during the analysis of domes. To investigate the effects of the initial defect, geometric nonlinearity, and material nonlinearity on the stability performance of different dome structures, 60 m numerical models were built and optimized by an iterative force-finding APDL program. Then, linear buckling analysis, geometric nonlinear stability analysis, geometric nonlinear stability analysis with initial defects, and dual nonlinear analysis with initial defects were discussed to compare the stability performance of ridge-beam cable domes (RCDs), suspen-domes, and conventional cable domes via finite element analysis. The results show that the buckling loads all follow the order of initial defect + dual nonlinear analysis < initial defect + geometric nonlinear analysis < geometric nonlinear analysis < linear buckling. The addition of ridge beams improves the overall stability and transforms the instability modes from local concave instability to overall torsional buckling. The ultimate load amplification coefficients of the RCD are close to those of the suspen-dome, while the vertical displacements of the RCD are more than those of the conventional cable dome, so the RCD has sufficient stiffness to reduce local displacement. Under 2–3 load combinations, internal ridge beams change from a tensile-bending state to a compressive-bending state, causing the entire instability of the RCD afterwards.

Numerical Investigation of the Relationship between Anastomosis Angle and Hemodynamics in Ridged Spiral Flow Bypass Grafts

Bypass graft failures are linked to hemodynamic disturbances resulting from poor design. Several studies have tried to improve graft patency by modifying conventional graft designs. One strategy being employed is to induce spiral flow in bypass grafts using an internal ridge which has been proposed to optimize blood flow. However, there is still no study focusing on how the anastomosis angle can affect the hemodynamics of such a design despite its huge influence on local flow fields. To fill this gap, we aimed to understand and optimize the relationship between anastomosis angle and ridged spiral flow bypass graft hemodynamics to minimize disturbances and prolong graft patency. Steady-state, non-Newtonian computational fluid dynamics (CFD) analysis of a distal, end-to-side anastomosis between a ridged graft and idealized femoral artery was used to determine the anastomosis angle that would yield the least hemodynamic disturbances. Transient, pulsatile, non-Newtonian CFD analysis between a conventional and ridged graft at the optimal angle was performed to determine if such a design has an advantage over conventional designs. The results revealed that smaller anastomosis angles tend to optimize graft performance by the reduction in the pressure drop, recirculation, and areas in the host artery affected by abnormally high shear stresses. It was also confirmed that the modified design outperformed conventional bypass grafts due to the increased shear stress generated which is said to have atheroprotective benefits. The findings of the study may be taken into consideration in the design of bypass grafts to prevent their failure due to hemodynamic disturbances associated with conventional designs and highlight the importance of understanding and optimizing the relationship among different geometric properties in designing long-lasting bypass grafts.

A unique case of commensalism: The beaver beetle Platypsyllus castoris (Leiodidae, Coleoptera) and its morphological adaptations.

Platypsyllus castoris is closely associated with beavers and displays a unique set of structural specializations. We document the morphology of adults with modern techniques, and interpret evolutionary changes linked with the specific life style. The small subfamily Platypsyllinae has evolved an entire suite of features correlated with a more or less close association with mammals, for instance a flattened body, a dorsal cephalic shield, flightlessness, eye reduction, and depigmentation. Within this small group, Platypsyllus displays numerous autapomorphic features, correlated with a close association with the beaver. Essential is a combination of mechanical stabilization and firm anchorage on the host, and efficient forward movement in the fur. Exo- and endoskeletal structures of the head and thorax are reinforced by vertical cuticular columns and by an array of internal ridges. The antennae are shortened and strongly modified, the mandibles distinctly reduced and flattened, unsuitable for cutting, scraping or grinding. The musculature of the mouthparts is simplified, whereas an enhanced set of prepharyngeal and pharyngeal dilators forms an efficient sucking pump. The prothoracic musculature is strongly developed. In contrast, the pterothoracic muscle system is distinctly simplified, even though leg muscles are strongly developed. Using the legs, the flattened beetles move sideways through the dense fur of the beaver, using posteriorly directed groups of setae and ctenidia to prevent being pushed backwards by the densely arranged hairs. In contrast to the anterior body, the cuticle of the abdomen is thin, and the entire tagma flexible, with thin layers of segmental muscles. The hind gut is not connected with the mid gut. The beetles probably consume liquid, possibly with emulgated minute skin debris. As the morphology of the mouthparts excludes damage to the skin of the host, the association should not be addressed as ectoparasitic but as commensalism.

Experimental and numerical study of swirl impingement cooling for turbine blade leading edge with internal ridged wall and film extraction holes

This paper presents a comparative experimental and numerical study of the internal heat transfer and pressure loss of swirl impingement cooling for turbine blade leading edge with internal ridges and film extraction holes. The leading edge cooling study includes a typical impingement cooling with centerline normal jets, a swirl impingement cooling with offset jets, and a swirl impingement cooling with offset jets and ridged wall. The normal jets are arranged at the impingement plate centerline, and the offset jets adopt a staggered arrangement alternatively on the lateral sides of the impingement plate. The ridged concave wall features two small semi-circular ridges symmetrically on opposite sides under the offset jets. Three rows of film holes are arranged symmetrically on the leading edge cavity, and another two rows of film holes are arranged on the opposite cavity wall behind. Transient thermochromic liquid crystal (TLC) experiments are conducted to obtain the detailed heat transfer distributions on the internal surface of the leading edge cavities with different cooling configurations. The results show that in the swirl impingement cooling, the swirling flow induced by the offset jets impinging onto the concave wall improves the streamwise heat transfer uniformity on the leading edge internal wall, which overcomes the limitation of large heat transfer non-uniformness between jet stagnation region and surrounding regions in typical normal jet impingement cooling. In the swirl impingement cooling with ridged wall, the near-wall jet interacts with the ridges on the concave wall and develops more widely along the spanwise directions, which greatly improves the spatial heat transfer uniformity. In addition, the ridges on the wall can also induce near-wall jets to separate from the wall and attach to the opposite concave wall, which produces low-velocity recirculation in the leading edge cavity and improves the capability and uniformity of coolant outflow through the film holes. Compared to the normal jet impingement cooling, the heat transfer of swirl impingement cooling with smooth and ridged wall can be increased respectively by 10.8%–14.0% and 10.9%–23.6% for the jet Reynold number from 20,000 to 50,000. In addition, the pressure loss is also reduced slightly by less than 5% in the swirl impingement cooling. As supplements to the experiments, numerical computations provide more insights into the turbulent flow structure in the leading edge cooling configurations.

RISKS OF DEVELOPMENT OF ANASTOMOTIC SUTURE FAILURE DEPENDING ON THE METHOD OF DISSECTION OF THE TISSUES OF THE ORGANS OF THE GASTROINTESTINAL TRACT AND THE FEATURES OF THEIR FORMATION

Summary. The purpose of the study: experimental and clinical study of the peculiarities of the course of reparative processes in the area of gastro- and colostomy wounds after carrying out various types of dissection and justification of the technique of forming anastomoses of the gastrointestinal tract.
 Research materials and methods. The paper presents the results of an experimental and clinical study of the processes occurring in the area of gastro-, entero-, and colostomy wounds made with electrosurgical or ultrasonic scalpels, immediately after exposure to tissues and within thirty days.
 Research results. Data were obtained that indicate a significant difference in destructive and reparative processes after various types of dissection. The use of ultrasonic dissection made it possible to maximally reduce ischemia of tissues and the internal ridge of anastomoses, in connection with which the reparative processes proceeded favorably and the patency through the anastomosis was not disturbed. The obtained results made it possible to scientifically substantiate the necessary distance of the needle from the edge of the dissection, depending on the type of dissection of the wall of the gastrointestinal tract.
 Conclusions. Ultrasonic dissection of the gastrointestinal tract is characterized by a relatively gentle effect on biological tissues, which is accompanied by the formation of much smaller areas of necrosis and necrobiosis than with electrosurgical exposure. In addition, biological welding of the edges of the wound, reliable hemostasis is achieved; there are no carbonization of fabrics, their sticking to the surface of the manipulator, smoke, sparks and other effects.
 It was established that after electrosurgical dissection, the phenomenon of prolonged necrosis develops, i.e., the necrosis zone spreads within three days, including due to the necrobiosis zone. This fact must be taken into account when applying seams.
 Adherence to the technical rules for the formation of gastrointestinal anastomoses, based on experimental data, made it possible to eliminate the risks of developing postoperative complications, first of all, their failure.

Bychowskicotylids (Monogenoidea: Gastrocotylinea) infecting the gills of the sweetlips Diagramma labiosum Macleay (Haemulidae) in Moreton Bay, Queensland, Australia, with the proposal of Lebedevia n. gen. and description of Lebedevia lebedevi n. sp.

Two species of Bychowskicotylidae (Monogenoidea: Gastrocotylinea) were collected from the gills of the sweetlips Diagramma labiosum Macleay (Haemulidae) obtained from Moreton Bay, Queensland, Australia, during January 2016. Lebedevia n. gen. is proposed for bychowskicotylids having 1) a bilaterally symmetrical haptor with four pairs of gastrocotylid-like clamps and lacking an armed lappet (anchors and hooks absent); 2) longitudinal sclerotized internal ridges lining the vas deferens, 3) an unarmed male copulatory organ, and 4) four interconnected vesicles located posterior to the genital atrium and lying on the body midline dorsal to the uterus and ventral to the vas deferens. Lebedevia lebedevi n. sp., the type and only species of the genus, is described, and Tonkinopsis transfretanus Lebedev, 1972 is recorded for the first time in Moreton Bay. Yamaguticotyla Price, 1959 (Bychowskicotylidae) is considered nomen nudum, and the authorship of the genus is corrected to Yamaguticotyla Yamaguti, 1963.

Morphological Re-description of Camallanus polypteri) Nematoda: Camallanidae) Infecting the African Sharptooth Catfish Clarias gariepinus (Clariidae).

Fish represents one of the major sources of animal proteins, and different species of fish are susceptible to infections with parasites which cause severe tissue damage and cell destruction of the infected organ. Therefore, in 2019, this parasitological study was conducted to assess the helminth parasites infecting the African sharptooth catfish Clarias gariepinus that were collected from Lake Manzala, Egypt. Only nematode parasite was reported as a prevalent infection from the fish stomach with an infection rate of 7.5%. Depending on the seasonal prevalence, the extent of the infection was analyzed. It was indicated that parasite infection was only reported as 15% in the winter season. Morphological and morphometric analyses of the present parasite species revealed that it possesses all the characteristics of the Camallanus genus, whereas it is closely related to Camallanus polypteri described previously. It is characterized by the presence of a buccal capsule with longitudinal internal ridges, some of which are very short and ranged from 8-14 in males and 8-9 in females. The esophagus consisted of muscular and glandular portions, the middle position of the excretory pore to the muscular esophagus, the anterior location of deirids to the nerve ring, posterior end of males with two unequal spicules and caudal papillae; nonetheless, it is smooth and straight in females. In addition, some morphology and measurement differences for the different body parts were identified with other Camallanus species. Therefore, the present study can provide a full morphologically re-description of Camallanus polypteri with a new geographical location in the Egyptian freshwater.

Characteristics and origins of ridges and troughs on the top of the Middle Miocene strata in the Beijiao Sag of the Qiongdongnan Basin, northern South China Sea

Sedimentary structures generated by (deepwater) bottom currents are of interest to geologists. Based on the root mean square, coherence attribute, and 3D representations, ridges and troughs are imaged for the first time using 3D high-resolution seismic data and confirmed by a well, YL19-1-1, in the Beijiao Sag of the Qiongdongnan Basin. Combined with 2D seismic profiles, we define the flow direction of bottom currents resulting in ridges and troughs. The results indicate that ridges and troughs occur on the top of the Middle Miocene strata and dominantly present wave-shaped structures. Their magnitudes decrease toward the upper and lower slopes. They extend for tens of kilometers, dominantly parallel to one another, with an evenly spaced distribution, some of which locally merge and bifurcate. They are aligned obliquely to the regional slope. The internal ridges are characterized by internal mounded reflections and/or parallel underlying-strata reflections. The presence of polygonal faults and weak to moderate amplitudes within the ridges and troughs suggests that they consist of fine-grained mudstones, as confirmed by the well YL19-1-1. High amplitudes filled within troughs are probably composed of coarse-grained turbidite materials, where polygonal faults are inhibited. Truncations and onlaps occur along the thalweg of a trough and are also clearly observed on the flanks of ridges and the walls of troughs. We infer that the troughs are a product of the erosion of bottom currents and the ridges are remnant underlying (sediment waves) strata as a result of the redeposition of eroded sediments. In addition, troughs are filled by turbidite materials with high amplitudes in the southwestern area of the 3D seismic survey, where ridges and troughs are a combined result of the early erosion by bottom currents and the later reworking by turbidity flows. We have developed conceptual schematic models to indicate the evolutionary history of the ridges and troughs. It provides new insights into the further understanding of the erosional and depositional impacts of bottom currents.

VP25.10: Fetal MRI findings of unilateral internal auditory canal enlargement and prominent posterior petrous ridge: an additional feature of PHACES syndrome

VP25.10: Fetal MRI findings of unilateral internal auditory canal enlargement and prominent posterior petrous ridge: an additional feature of PHACES syndrome

THE MATURE LARVA OF THE SOUTH AMERICAN CLEPTOPARASITIC BEE THALESTRIA SPINOSA (FABRICIUS) (APIDAE: NOMADINAE: EPEOLINI)

This paper describes and illustrates with diagrams and photographs the diapausing larva of the epeoline Thalestria spinosa (Fabricius), a large cleptoparasitic bee, recovered in 1971 from the nest of its host, the South American andrenid bee Oxaea flavescens (Klug). The larva closely resembles that of many Triepeolus (Epeolini), the immature stages of which are better known (Rozen, 1966, 1996). The larva of T. spinosa can be distinguished from those of other known Epeolini by the shape of its short, triangular mandible with a pronounced swelling on its inner surface that projects distally from its base. The lack of strong tentorial structuring as well as internal ridges on the cranium has long suggested that epeolines have a weak head exoskeletons. However, after careful study of T. spinosa and review of other larval Epeolini, the author now suggests that the extensive integumental thickening of the cranium and the broad connections of the frontal area of the head with the rear part, though less noticeable, obviates the need of a strong tentorium and internal head ridges.

Geomorphologic and Glacial Evolution of the Cachapoal and southern Maipo catchments in the Andean Principal Cordillera, Central Chile (34°-35º S)

We present here a reconstruction of the post late Miocene landscape evolution of the western slope of the Andean Cordillera Principal near 34°20’ S. We base our analysis on the available geological information, a morphological characterization of the landform assemblages in the Cachapoal and southern Maipo catchments, and the first 10Be exposure ages for moraines in this area. The Cachapoal drainage basin is characterized by a variety of morphological features, like an elevated low-relief surface, volcanoes and lava flows on valley slopes, U-shaped valley sections, roches moutonnées, and large glaciated areas. Different kinds of deposits have been included in the study, such as moraines, lacustrine and landslide deposits, and a well-developed system of fluvial terraces in the more distal part of the Cachapoal catchment. Landslides are mostly developed on rocks of the late Eocene-early Miocene Abanico Formation. and are less frequent in outcrops of the overlying, early to middle Miocene Farellones Formation. We estimate that the lowest end moraine in the Cachapoal catchment is located next to the locality Bocatoma Chacayes (~950 m altitude), though covered by a major landslide. No evidence exist for glacial deposits further down stream in this region. Lateral moraine ridges of the Cachapoal Glacier at Los Cerrillos yielded 10Be exposure ages of 20.3±2.9 and 21.9±5.3 ka that indicate they are associated with the Last Glacial Maximum (LGM). Holocene moraines exist next to all glacier tongues. Of particular interest in this region is the 12 km-long debris-covered Cachapoal Glacier, the longest valley glacier in the central Chilean Andes, and its distal and proximal moraine deposits. Two lateral moraines adjacent to the present-day Cachapoal Glacier yielded exposure average ages of 13.5±2.4 ka for the external ridge, indicating the Younger Dryas, and 3.8±0.8 ka for the internal ridge, an age that coincides with the 4.2 ka global climatic event that marks the beginning of the Meghalayan Age, at the end of the Holocene. The large size of this moraine on both sides of the ice tongue indicates the great development of the glacier at that time. Some of these ages coincide with ages obtained further north in the Maipo drainage basin, at the latitude of Santiago, and in the eastern flank of the cordillera, however, no pre-LGM deposits were found here, unlike the other mentioned regions. This difference together with the much lower altitude of the LGM moraine deposits in the study region suggests that the Cachapoal catchment is a transition zone to a more humid region further south, and indicates the great need for further reconnaissance and dating of glacial deposits in this Andean region. Our analysis of the geomorphological evolution is consistent with incision start for the Cachapoal Valley in latest Miocene. In this process, glacier incision was apparently not much effective until mid-Pleistocene time, when volcanism was active in the higher regions of the mountain range covering areas not yet incised, whereas in the western Principal Cordillera lavas flowed in deeply incised valleys. Pleistocene glaciers deepened and shaped the already incised valleys, which are presently mostly occupied by rivers.

Surviving the marine environment: two new species of Mallomonas (Synurophyceae)

ABSTRACTThe genus Mallomonas consists of single-celled flagellates covered with siliceous scales and bristles and is well known in freshwater environments. Two new marine Mallomonas species were collected from Dongho Beach, Jeollabukdo, Korea. To fully understand the taxonomy of the new species, we performed molecular phylogenetic analysis based on a concatenated dataset and observed morphological features using light and electron microscopy. For the phylogenetic analysis, we used a combined dataset from five gene sequences: nuclear small subunit (SSU) and large subunit (LSU) rDNA and plastid LSU rDNA, rbcL and psaA genes. The new species M. cuspis sp. nov. grouped with M. heterospina and M. oviformis in the section Planae. It had scales with a broad shield marked with V-shaped internal ridge that lacked submarginal ribs and a dome. The other new species, M. marina sp. nov., clustered with M. cratis, M. pseudocratis, M. asmundiae and M. striata var. serrata in section Striatae and had scale characters that matched the group, including a well-developed posterior submarginal rib and series of transverse ribs on the shield and dome. In addition, we investigated the effect of salinity on growth rate and cell morphology. The two marine species represented high growth rate between salinities of 10 and 30 psu, suggesting that both species are well adapted in marine environments. When exposed to salinities of 0 and 5 psu, they underwent cell enlargement.

Automatic technical documentation of lithic artefacts by digital techniques

Despite the existence of a wide variety of standards to create hand-made illustrations of lithic artefacts, the conventional process is laborious, time-consuming and the quality of the drawings is highly variable. In this paper, a novel computer-based methodology to create automatic technical documentation of lithic artefacts, in the form of manual-like drawings, is presented. The method exploits the artefact digital model obtained by a 3D optical scanner. An optimization process is proposed to orient the digital model reproducing the conventional positioning. A lighting model is used to introduce an illumination source having different directions, to highlight surface details. A set of images is then created and segmented to retrieve the artefact outline and the internal ridges between flake scars. Potentialities of the proposed methodology are illustrated by analyzing three different stone artefacts acquired by a structured light scanner. 2D technological drawings are automatically created and compared to those obtained by an experienced lithic illustrator.

Attenborites janeae: a new enigmatic organism from the Ediacara Member (Rawnsley Quartzite), South Australia

Attenborites janeae gen. et sp. nov., is a new enigmatic fossil from the Ediacara Member of the Rawnsley Quartzite, South Australia. Attenborites is a well-defined irregular oval to circular fossil preserved in negative hyporelief ranging in length from 4.5–24 mm. Preserved internal grooves and ridges, variable in number and running parallel to the long axis, typically converge towards one end of the specimen. This taxon is unlike any previously described both in terms of overall morphology and in terms of the irregular nature of the outer and inner morphology. While there are no direct morphological characters that suggest that this organism was pelagic, the nature of preservation suggests that a pelagic lifestyle should at least be considered. However, it is not possible to say whether this animal was likely a ctenophore, cnidarian or a pelagic organism of unknown affinity.

Modified Medial Ramus Retractor to Facilitate Horizontal Osteotomy During Sagittal Split Ramus Osteotomy Procedure.

Introducing a horizontal osteotomy is the first and a critical step in sagittal split ramus osteotomy procedure. Identification of the lingula and medial displacement of the vital structures entering the inferior alveolar foramen are of paramount importance in ensuring a risk-free placement of the medial cut with bur or a saw. Quite often, identification of lingula and retrolingular fossa can be an arduous task owing to the thickness of the internal oblique ridge. Hence, placement of horizontal osteotomy depends on the experience of the operator.Here, the authors describe a simple, low profile instrument that aids in the identification of the lingula as well as provide a posterior stop for horizontal osteotomy during the sagittal split ramus osteotomy procedure.

Lithobius (Chinobius) yuchernovi, a new lithobiid species from northeastern Siberia and the Kamchatka Peninsula, Russia (Chilopoda, Lithobiomorpha).

Lithobius yuchernovi sp. n. is described, based on type material from the Ola Plateau, Magadan Region, Russia. The new species is widely distributed in northeastern Siberia, ranging from the Magadan Region, until the eastern Chukot Autonomous Region and the Kamchatka Peninsula in the southeast, whence non-type material is documented. This species belongs to the subgenus Chinobius Matic, 1973 based on the structure of the female gonopodal claw (more than two denticles on the internal ridge). It differs from all Palearctic species of the genus Lithobius by the following apomorphy: distoventral tubercle supporting a cluster of long and curved setae situated on the last male tibia. In addition, it shows dorsal and ventral sulci on the last legs. New replacement names are introduced: Lithobius zachiui nom. n. for Lithobius (Chinobius) orientalis (Matic, 1973) and Lithobius carli nom. n. for Lithobius (Alokobius) orientalis Attems, 1953.

Optimisation of a Novel Spiral-Inducing Bypass Graft Using Computational Fluid Dynamics

Graft failure is currently a major concern for medical practitioners in treating Peripheral Vascular Disease (PVD) and Coronary Artery Disease (CAD). It is now widely accepted that unfavourable haemodynamic conditions play an essential role in the formation and development of intimal hyperplasia, which is the main cause of graft failure. This paper uses Computational Fluid Dynamics (CFD) to conduct a parametric study to enhance the design and performance of a novel prosthetic graft, which utilises internal ridge(s) to induce spiral flow. This design is primarily based on the identification of the blood flow as spiral in the whole arterial system and is believed to improve the graft longevity and patency rates at distal graft anastomoses. Four different design parameters were assessed in this work and the trailing edge orientation of the ridge was identified as the most important parameter to induce physiological swirling flow, while the height of the ridge also significantly contributed to the enhanced performance of this type of graft. Building on these conclusions, an enhanced configuration of spiral graft is proposed and compared against conventional and spiral grafts to reaffirm its potential benefits.

Les indices climatiques du Pléistocène supérieur et de l’Holocène des formations quaternaires de la côte atlantique (Rabat-Témara, Maroc)

The area of Rabat-Témara is known for a very important quaternary sedimentary archives, which are found in the form of marine and continental deposits preserved along the Atlantic coast and also, as sedimentary filling in the cavities shaped in the calcarenites coastal ridge. The last dates on these sediments show that this karst filling covers the upper Pleistocene and the Holocene. The excavation of the cave of El Hahroura 2 shows a fairly homogeneous filling over the 3m. This constancy at the filling indicate a more or less identical climate from the layer 11 to the layer 2, which is mainly arid, with slight variations expressing wet and fresh climatic pulsations. The upper part of El Harhoura, attributed to the recent Neolithic, agrees with a setting in an environment corresponding to a return to wet climatic conditions. The study of the environments of the prehistoric caves shows that at the time of the installation of the humans on the Atlantic coast, the quaternary landscape is similar to the present one. The formation of the most littoral ridge was made during the isotopic stage 5, with formation of dunes fixed by vegetation and cemented by a carbonate bond. This ridge, more or less parallel to the coast, formed under wet climatic conditions already described in the filling of caves, with nevertheless warm recurrences. The installation of this ridge will contribute to the closure of the pre-existing coastal plain and leads to the formation of an oulja, open to the sea in favor of the lagoons. This oulja will host high-level marine deposits characterized by a mixture of marine and continental fauna. The dates of the deposits of the oulja and the internal ridge, in progress, will enable us to determine the age of cave digging; they will also help to determine the climatic phases prior to the settlement of prehistoric men in the region of Rabat-Témara.

Inequalities for Left Atrial Ablation.

Great teaching value can come from showcasing an unusual phenomenon that serves as an aid to explain how best to approach mundane, common problems. In this installment of teaching rounds, Wakabayashi et al1 use an unusual activation sequence observed along the mitral annular atrial myocardium that was observed after ablation of the mitral isthmus to teach us about the pitfalls created by the complex terrain in the left atrium (LA). See Article Much of what we initially learned about linear ablation is from ablation of the cavotricuspid isthmus for typical right atrial flutter. Although this experience is helpful, we need to be alert to the fact that we cannot equate this relatively simple ablation approach to the complex-interlinked isthmus anatomy in the LA. In their approach to this complex and instructional case, the authors stress the initial importance of pulmonary vein isolation when approaching mitral isthmus–dependent flutter. Unlike the human inferior vena cava, the left lower pulmonary vein does not serve as an anchor point for ablation of the mitral isthmus. This is because of the myocardial sleeves that extend into this pulmonary vein. As a result, to truly anchor the mitral isthmus line and obtain isthmus block at this site, either the ablation needs to go into the pulmonary vein (which would have a prohibitive risk of pulmonary vein stenosis) or the pulmonary vein must be circumferentially isolated with LA ablation. The usual method for determining whether the pulmonary vein is indeed isolated …