Transverse Flexure Research Articles

Experimental and statistical study on the effect of process parameters on the quality of continuous fiber composites made via additive manufacturing

Ongoing research in additive manufacturing towards structural and industrial application has led to the use of commingled roving as a manufacturing feedstock for printing high fiber volume fraction composites. The prospects of using this technology for high performance applications necessitates the need for a comprehensive experimental investigation into the effects of processing parameters on the quality of an additively manufactured composite printed from commingled roving feedstock. In this work, transverse flexure and void fraction matrix pyrolysis testing are both performed to evaluate composite quality. The transverse flexure test is a testing approach that evaluates the quality of the interfacial fiber-matrix bond while the void fraction test estimates the void content in the printed composite. A full observational study consisting of 27 different test combinations is done to investigate the effects of three different process parameters namely, temperature, pressure, and print speed across three different levels. Composite samples were made from commingled roving of E-glass and amorphous PET using an in-house built continuous fiber composite digital manufacturing system. Least squares regression analysis is performed to study the main, interaction and quadratic effects of process parameters. A statistical regression model having an R2 adjusted value of 80.1% is generated from the transverse flexure study, which is used to explain main and interaction effects and also predict performance. Response surface plots are also generated and are used to optimize process parameters which can subsequently be of help in scaling up composite manufacturing. Results show that all three process parameters are highly statistically significant at the 0.01 level of significance. Pressure * Temperature and Pressure * Printspeed are significant interaction terms. Pressure plays a weightier role when print speed is increased or temperature is decreased as it closes more voids that would ordinarily have been introduced because of drop in polymer melt viscosity. Micrographic analysis is also performed.

Densification and grain growth kinetics of boron carbide powder during ultrahigh temperature spark plasma sintering

Dense B4C material was fabricated using spark plasma sintering (SPS), and the densification mechanisms and grain growth kinetics were revealed. The density, hardness, transverse flexure strength and toughness of samples were investigated and the model predictions were confirmed by SEM and TEM experimental observations. Results show that SPSed B4C exhibits two sintering periods: a densification period (1800–2000 °C) and a grain growth period (2100–2200 °C). Based on steady-state creep model, densification proceeds by grain boundary sliding and then dislocation-climb-controlled mechanism. Grain growth mechanism is controlled by grain boundary diffusion at 2100 °C, and then governed by volume or liquid-phase diffusion at 2200 °C.

Vascular variations encountered during laparoscopic surgery for transverse colon, splenic flexure, and descending colon cancer: a retrospective cohort study

BackgroundLaparoscopic surgery for cancer located in the transverse colon or splenic flexure is difficult because of vascular variability in this region and adjacent vital organs such as the pancreas, spleen, and duodenum.MethodsThis retrospective cohort study involved 51 patients who underwent laparoscopic surgery for colon cancer at Tokushima University Hospital from July 2015 to December 2020. Variations of the middle colic artery (MCA), left colic artery (LCA), middle colic vein (MCV), and first jejunal vein (FJV) and short-term outcomes of laparoscopic surgery in patients with each vascular variation were evaluated.ResultsVariations of the MCA, LCA, MCV, and FJV were classified into four, three, five, and three patterns, respectively. The short-term outcomes of laparoscopic surgery for transverse colon cancer in patients with MCA variations and those with FJV variations were evaluated, and no significant difference was found in the operation time, blood loss, postoperative complication rate, time from surgery to start of dietary intake, or time from surgery to discharge among the different variations. Additionally, no significant differences were found in the short-term outcomes of laparoscopic surgery for descending colon cancer in patients with LCA variations.ConclusionPreoperative assessment of vascular variations may contribute to the stability of short-term outcomes of laparoscopic surgery for transverse colon, splenic flexure, and descending colon cancer.

Pneumatosis cystoides intestinalis in a trauma patient presenting with pneumoperitoneum: a case report

BackgroundPneumatosis cystoides intestinalis is a rare and usually benign condition in which multiple thin-walled cysts develop in the submucosa or subserosa of the gastrointestinal tract. While usually asymptomatic, severe cases can result in pneumoperitoneum, which can be managed surgically or medically depending on circumstances. We present a case of a patient with pneumatosis cystoides intestinalis, which presented as pneumoperitoneum following trauma. To our knowledge, there are no other published cases in which a trauma patient with pneumoperitoneum was found to have radiologic evidence of pneumatosis cystoides intestinalis.Case presentationWe present the case of a 37-year-old Hispanic male admitted to the hospital after being involved in a motorcycle accident. Computed tomography imaging of the abdomen and pelvis with oral and intravenous contrast demonstrated trace pneumoperitoneum, possibly originating from the splenic flexure of the colon without evidence of extravasation of oral contrast. Laparoscopy with conversion to exploratory laparotomy revealed bowel abnormalities at the distal transverse colon and splenic flexure, which were identified as pneumatosis cystoides intestinalis by pathology. There was no evidence of bowel perforation. A panel of abdominal radiologists attended the computed tomography interpretation to note that incidental atraumatic or traumatic rupture of the cysts could have caused the pneumoperitoneum. The patient had an uncomplicated postoperative course and was transferred to another facility per insurance request.ConclusionsWhen presenting in the context of trauma, pneumatosis cystoides intestinalis can lead to difficult management decisions. To our knowledge, there are no existing evidence-based guidelines for the scenario of concurrent pneumatosis cystoides intestinalis, blunt abdominal trauma, and pneumoperitoneum in a patient with a benign abdominal exam. This patient’s pneumoperitoneum was likely caused by rupture of preexisting cysts rather than frank bowel perforation. Patients who are asymptomatic, lack signs of clinically worrisome disease, and have a low pretest probability will likely not benefit from surgery and can be medically managed. Thorough discussion between surgeons and radiologists can be helpful when evaluating the clinical significance of a patient’s pneumatosis cystoides intestinalis and aid in the decision to perform surgery.

Colonic Volvulus

Colonic volvulus accounts for 3 to 5% of bowel obstructions in the United States. Current data reveal sigmoid volvulus as the most common colonic volvulus, followed by volvulus of the cecum, transverse colon, and splenic fixture. Despite a low incidence in the United States, diagnosis, management, and patient outcome depend on an appropriate index of suspicion and adherence to the proposed algorithm highlighting the approach to the patient with colonic volvulus. This review outlines the definition, pathogenesis, and epidemiology of colonic volvulus, as well as its clinical evaluation and treatment. Tables review the demographics of colonic volvulus in the United States, the differential diagnosis of and risk factors for colonic volvulus, important radiographic findings in colonic volvulus, and nonoperative management of sigmoid volvulus. Figures show the types of ileosigmoid knot; plain radiographs of cecal, sigmoid, transverse, and splenic flexure volvulus; contrast enema of cecal, transverse, splenic flexure, and sigmoid volvulus; cross-sectional abdominal imaging of cecal, sigmoid, and transverse colon volvulus and ileosigmoid knot; endoscopic evaluation in sigmoid volvulus; use of an esophageal overtube for placement of a rectal tube; necrotic cecum and transverse colon volvulus in the operating suite; and sigmoid volvulus in an elderly gentleman. This review contains 14 figures, 13 tables, and 165 references Keywords: Colonic volvulus, colonic obstruction, endoscopy, surgical intervention, ileosigmoid knot, splenic flexure volvulus, sigmoid volvulus, transverse colon volvulus, cecal volvulus

Primary tumor resection improves prognosis of unresectable carcinomas of the transverse colon including flexures with liver metastasis: a preliminary population-based analysis

PurposeStudies on unresectable colorectal cancer liver metastasis(CRLM) rarely analyze the prognosis of the patients from the point of colonic subsites. We aimed to evaluate the effect of primary tumor resection (PTR) and different scope of colectomy on the prognosis of patients with unresectable transverse colon cancer liver metastasis (UTCLM), hepatic flexure cancer liver metastasis (UHFLM), and splenic flexure cancer liver metastasis (USFLM).Patients and methodsThe patients were identified from the Surveillance, Epidemiology, and End Results (SEER) database from 2010 to 2015. Cox proportional hazards regression models were used to identify prognostic factors of overall survival (OS) and cause-specific survival (CSS). Kaplan-Meier analyses and log-rank tests were conducted to assess the effectiveness of PTR on survival.ResultsIn total, this study included a cohort of 1960 patients: 556 cases of UHFLM, 1008 cases of UTCLM, and 396 cases of USFLM. The median survival time of whole patients was 11.0 months, ranging from 7.0 months for UHFLM patients to 15.0 months for USFLM patients. USFLM patients had the best OS and CSS, followed by UTCLM patients. UHFLM patients had the worst OS and CSS (All P < 0.001). PTR could improve the OS and CSS of UTCLM, UHFLM, and USFLM (All P < 0.001). Subgroups analysis revealed that USFLM patients with tumor size≤5 cm and negative CEA had not demonstrated an improved OS and CSS after PTR. Multivariate analysis showed that PTR and perioperative chemotherapy were common independent prognostic factors for UHFLM, UTCLM, and USFLM patients. There was no difference between segmental colon resection and larger colon resection on CSS of UHFLM, UTCLM, and USFLM patients.ConclusionsWe confirmed the different survival of patients with UTCLM, UHFLM, and USFLM, and for the first time, we proved that PTR could provide survival benefits for patients with unresectable CRLM from the perspective of colonic subsites of transverse colon, hepatic flexure, and splenic flexure. Besides, PTR may not improve the prognosis of USFLM patients with CEA- negative or tumor size≤5 cm. For oncologic outcomes, we concluded that segmental colon resection seemed an effective surgical procedure for UTCLM, UHFLM, and USFLM.

A case of inflammatory pseudotumour of the gallbladder presenting as a big mass of uncertain behavior

BackgroundInflammatory pseudotumour has been used to describe an inflammatory or fibrosing tumoral process of an undetermined cause that may involve a variety of organ systems, including the lungs, spleen, liver, lymph nodes, pancreas and extrahepatic bile duct with potential for recurrence and persistent local growth. In this article, we report a patient with a big mass of uncertain nature and behavior.Case presentationA 60-year-old woman presented with a 1-week history of abdominal pain, fever and jaundice. Six months before she had had right upper quadrant pain that was interpreted as biliary colic. A contrast-enhanced CT scan showed a big mass of soft tissue with diffuse infiltration of the gallbladder, displacement of the transverse colon, hepatic flexure and duodenum. For diagnostic distinction between a chronic inflammatory disease or a neoplasm, exploratory laparotomy was required. Intraoperative exploration disclosed a big mass of hard texture involving the gallbladder, with multiple concrements, hepatoduodenal ligament, right and transverse mesocolon, stomach and duodenum.Cholecystectomy was performed, preserving adjacent organs with macroscopic desmoplastic reaction. Histopathologic examination of the gallbladder showed a spindle cell proliferation with diffuse chronic inflammatory infiltrate of lymphocytes, plasma cells and hyalinized fibrous stroma. No vascular invasion or cellular atypia were evident.ConclusionInflammatory pseudotumour is a rare condition and diagnostic distinction from a chronic inflammatory disease or other neoplasm is only possible by histopathologic examination. There is a limited number of case reports in the literature indicating tumor location in the gallbladder.

Exosomal marker CD63 expression pattern using immunohistochemistry (IHC) in patients with rectal adenocarcinoma in comparison with left-sided colon cancer.

e16096 Background: Adenocarcinomas arising from the distal one third of the transverse colon, splenic flexure, descending colon, sigmoid colon and rectum are often grouped together due to their hindgut embryologic origin and referred to as left-sided colorectal cancer (CRC). Rectal cancer represents a subset of CRC that has distinct differences in anatomical location, clinical behavior, prognosis and molecular background. In patients with left sided colon cancer (LSCC), the expression of exosomal marker CD63 was reported to be higher in the adjacent normal mucosa (ANM) compared to the tumor (224 vs 154, p = 0.0001). Here, we explored the pattern of CD63 expression using immunohistochemistry in patients with rectal cancer in comparison with patients with LSCC. Methods: Between 2015 and 2018, 53 patients underwent rectal cancer biopsy/resection and had available tissues for CD63 IHC staining. Two pathologists independently scored CD63 expression in the tumor and ANM. Staining intensity was graded from 1-3. Staining percentage was estimated in 10% increments. Mean quick-score (Q-score) was calculated (intensity x percentage). Paired t test was used for statistical analysis. Results: Median age was 60 (range 34-80). Females represented 26%. Caucasians and African Americans represented 74% and 26%, respectively. In patients with rectal cancer, the mean CD63 expression was higher in ANM compared to their expression in the tumor (147 vs 113, p = 0.0012). Compared to patients with LSCC (N = 30), the mean CD63 expression in patients with rectal cancer was lower in the ANM (224 vs 147, p &lt; 0.0001) and in the tumor (154 vs 113, p = 0.01). Conclusions: In our cohort of patients with rectal cancer, exosomal marker CD63 expression was lower in tumor compared to ANM. This observation was similar to our previously reported findings in patients with LSCC. Compared to patients with LSCC, patients with rectal cancer had lower expression of CD63 in the tumor and ANM. To our knowledge, this is the first study to explore exosomal marker CD63 expression using IHC in patients with rectal cancer.

Straightening of Relatively Flexible Cylindrical Parts. Part II. Stress State of the Cylinder Workpiece in Transverse Rolling between Flat Plates

The intended form of relatively flexible cylindrical parts (shafts and axles) may be restored by straightening by flexure under a distributed load, with subsequent strengthening of the workpiece by surface plastic deformation based on transverse rolling between flat plates. It is well known that the nonequilibrium stresses are generated in the whole workpiece after straightening by transverse flexure, and the part is eventually deformed again. Therefore, the workpieces should be additionally straightened with surface plastic deformation after straightening by flexure. We use transverse rolling by flat plates for that purpose. The aim in the present work is to determine the capture conditions and the stress state of the workpiece in transverse rolling of cylindrical parts between flat plates. The mathematical analysis is based on the theory of an elastoplastic solid; ANSYS Workbench software is employed. A new method is proposed for control of stress state in straightening of cylinderical workpieces. The limiting capture angle α ranging 2–8 degrees and the maximum absolute reduction depending on friction coefficient and on the diameter of workpiece are obtained. The optimum reduction varies ΔH = 0.07–0.15 mm. The calculation data show that the stress state of uniform extension occurs at the center in the workpiece cross section after transverse rolling, and the stress state of reduction is formed at the peripheral areas of the workpiece. The straightening method of transverse rolling between flat plates eliminates crack formation and destruction of the material in the central area of the cylindrical parts.

Straightening of Relatively Flexible Cylindrical Parts. Part I. Establishing the Loading Conditions in Transverse Straightening

Relatively flexible cylindrical parts (shafts and axles) may be straightened by loads produced by different stresses in different distributions. A promising method is straightening by flexure under a distributed load, with subsequent strengthening of the workpiece by surface plastic deformation based on transverse rolling between flat plates. The goal in the present work is to determine the stress state of the workpiece in transverse straightening so as to select the best type of load and treatment conditions. The mathematical analysis is based on the theory of an elastoplastic solid; ANSYS Workbench software is employed. Effective methods of loading in the transverse straightening of cylindrical parts are determined. Analytical calculations yield the residual stress corresponding to straightening of the cylindrical parts. The residual stress required for straightening depends on the initial flexure, the material in the workpiece, and its size. The stress state of cylindrical parts is determined for different types of transverse loading. The flexural stress for straightening of a shaft under a distributed load is less than the stress due to a transverse force. To straighten a rod (diameter 10 mm, length 200 mm) with initial flexure 0.5 mm, flexural stress of about 370 MPa must be created. In the transverse straightening of cylindrical parts, flexure under the action of a distributed load is an effective loading method. Limiting flexural coefficients of 5.3–5.5 are obtained for all values of the shaft rigidity in straightening by transverse flexure under a distributed load when l/L = 0.8. The proposed mathematical model correctly determines the residual stress corresponding to straightening of the cylindrical parts. The formula derived for calculating the total flexure and determining the effective load may be recommended for practical use in production conditions so as a ensure precise straightening of relatively flexible parts such as shafts.

Cyclic Tests of Stress-corrosion Cracks in Steel Gas Pipelines with No Corrosive Fluid

Stress-corrosion defects in the output pipeline of a compressor station are subjected to metallographic analysis and mechanical tests. The pipeline consists of pipe imported in the 1980s. Diagnostic data obtained in nondestructive monitoring of such pipelines are analyzed, and the effectiveness of various diagnostic methods in detecting stress-corrosion defects in large-diameter pipe is assessed. The grade of steel in the pipeline is identified. The cracks are identified by type and morphology, and their development is determined. Nonmetallic sulfide inclusions have no influence on pipeline failure in the stress-corrosion conditions considered. The sulfur content in the corrosion products is no more than the sulfur content in the metallic sample. In some samples, the sulfur content may be decreased except for local sections with nonmetallic sulfide inclusions. Electron-microscope images show that such nonmetallic inclusions do not promote failure. The results of cyclic tests of cracked samples cut from the pipeline are presented. The test conditions are selected in accordance with recent operating conditions of the compressor station. According to the results, pipe with defects at the initial stage of development exhibits considerable durability in the tests. In fact, the cracked samples withstand (1.6–7.5) × 106 cycles under transverse cyclic flexure in a single plane, in the absence of corrosive fluid. In practice, the number of such cycles is no more than 120–200 per year, in normal pipeline operation. Hence, a pipeline with stress-corrosion defects in their initial stage of development will last a long time if its metal wall is protected from the action of corrosive fluid.

Comparing the Impact Strength and Transverse Flexure Strength of Three Different Dentures Base Materials

Comparing the Impact Strength and Transverse Flexure Strength of Three Different Dentures Base Materials

Behavior of thin-walled prestressed concrete roof elements – Experimental investigation and numerical modeling

This paper presents an experimental investigation on thin-walled prestressed concrete roof elements, characterized by different shapes, test arrangements and failure modes (e.g. longitudinal and transverse bending or shear). The aim of this experimental program is to investigate roof elements behavior up to their ultimate capacity under different loading conditions, as well as to study second order effects and the influence of transverse flexure in the optimization of wing reinforcement. The response of tested roof elements is subsequently numerically analyzed, by adopting PARC constitutive model to perform non-linear finite element analyses (NLFEA), able to take into account the interaction between transverse and longitudinal bending, as well as geometric non-linearity. Finally, an application of the proposed numerical procedure for design purposes is also discussed.

Multi-mode traffic-induced vibrations in composite ladder-deck bridges under heavy moving vehicles

Composite (steel-concrete) ladder-decks represent one of the most common solutions in road bridges nowadays. In these structures the Serviceability Limit State (SLS) of vibrations is traditionally ignored or roughly addressed by means of simple static deflection-based approaches, inherently assuming that the vibrations are controlled by the fundamental longitudinal mode. This work demonstrates that a wide range of high-order vibrational modes, involving the transverse flexure of the slab between longitudinal girders, govern the accelerations recorded in the deck and inside the vehicles. In addition, a new methodology for analysing the Vehicle–Bridge Interaction is proposed, including the approaching platforms, the transition slabs, and the bridge joints. The results suggest that the riding comfort for vehicle users is specially affected by direct effects on the wheels, like the road roughness and possible construction misalignments at the bridge joints, as well as low-frequency vibrations coming from the deck in short or slender bridges. The filtering effects resulting from the average of the response in time and in space when calculating the root mean square acceleration are also explored, and new design parameters are provided. In addition, several structural features (such as the depth and spacing of the longitudinal and transverse steel beams, the thickness of the concrete slab, and the stiffness of the cantilever cross beams at the diaphragm sections) have been studied, and a set of new design criteria has been established. It has been demonstrated that the transverse flexibility of the deck (specially influenced by the support conditions and the slab thickness) is critically important for the users’ (pedestrians and vehicle passengers) comfort, as it controls the aforementioned high-order vibrational modes which govern the dynamic response.

Stress concentration in symmetric two-arm crank with transverse flexure

The stress concentration in a plane crank with a filled hole is considered, in the case of transverse flexure. The stress-concentration coefficient is expressed as a function of the tightness (gap), bending torque, transverse force, and relative width of the plate.

A nonlinear spring mechanism incorporating a bistable composite plate for vibration isolation

The High Static Low Dynamic Stiffness (HSLDS) concept is a design strategy for a nonlinear anti-vibration mount that seeks to increase isolation by lowering the natural frequency of the mount whilst maintaining the same static load bearing capacity. It has previously been proposed that an HSLDS mount could be implemented by connecting linear springs in parallel with the transverse flexure of a composite bistable plate — a plate that has two stable shapes between which it may snap. Using a bistable plate in this way will lead to lightweight and efficient designs of HSLDS mounts. This paper experimentally demonstrates the feasibility of this idea. Firstly, the quasi-static force–displacement curve of a mounted bistable plate is determined experimentally. Then the dynamic response of a nonlinear mass–spring system incorporating this plate is measured. Excellent agreement is obtained when compared to theoretical predictions based on the measured force–displacement curve, and the system shows a greater isolation region and a lower peak response to base excitation than the equivalent linear system.

Higher-order theory for bending and vibration of beams with circular cross section

This paper presents an efficient and simple higher-order theory for analyzing free vibration of cylindrical beams with circular cross section where the rotary inertia and shear deformation are taken into account simultaneously. Unlike the Timoshenko theory of beams, the present method does not require a shear correction factor. Similar to the Levinson theory for rectangular beams, this new model is a higher-order theory for beams with circular cross section. For transverse flexure of such cylindrical beams, based on the traction-free condition at the circumferential surface of the cylinder, two coupled governing equations for the deflection and rotation angle are first derived and then combined to yield a single governing equation. In the case of no warping of the cross section, our results are exact. A comparison is made of the natural frequencies with those using the Timoshenko and Euler–Bernoulli theories of beams and the finite element method. Our results are useful for precisely understanding the mechanical behavior and engineering design of circular cylindrical beams.

Flexural Behavior at Service and Ultimate Limit State of One-Way Concrete Slabs Reinforced with Corrosion-Resistant Reinforcing Bars

The paper presents the results of an experimental investigation of the structural performance and susceptibility to deformation of a concrete bridge deck with corrosion-resistant reinforcing (CRR) bars (i.e., bars that exhibit better corrosion resistance than traditional black steel when embedded in concrete). Flexural tests of one-way slabs were conducted to simulate negative transverse flexure over a bridge girder as assumed in the commonly used strip design method. Grade 60 (uncoated), epoxy-coated reinforcing Grade 60, Enduramet 32 stainless steel, 2304 stainless steel, MMFX2, and glass fiber–reinforced polymer bars were studied. The experimental program was designed to evaluate how flexural performance at service and ultimate limit states are affected by a one-to-one replacement of Grade 60 with CRR bars, a reduction of concrete top clear cover, and a reduction in rebar quantities in the top mat of the bridge deck. Moment–curvature predictions from Response 2000, a computer-based sectional analysis program, were consistent with the test results. This consistency demonstrated the viability of Response 2000 for use with high-strength and nonmetallic rebar without a defined yield plateau. The susceptibility of the specimens of concrete slab strips to deformation was defined with ultimate- to service-level ratios of midspan deflection and curvature. The susceptibility to deformation of the specimens of MMFX2 and Enduramet 32 stainless steel (one-to-one replacement) was consistent with the Grade 60 controls; this consistent response demonstrated that bridge deck slabs with high-strength rebar without a defined yield plateau still can provide sufficient ductility at an ultimate limit state. A reduction in rebar quantity and cover provided acceptable levels of ductility for the specimens of 2304 stainless steel and MMFX2-reinforced slabs.

Centrifuge modelling of temporary roadway systems subject to rolling type loading

Scaled centrifuge modelling techniques were used to study the soil-structure interactions and performance of a jointed rollable aluminium roadway (or trackway) system on soft clay under light truck tyre loads. The measured performance and subsequent analyses highlighted that the articulated connections significantly reduced the overall longitudinal flexural stiffness of the roadway leading to stress concentrations in the soil below the joints under tyred vehicle loadings. This resulted in rapid localised failure of the supporting soil that in turn led to excessive transverse flexure of the roadway and ultimately plastic deformations. It is shown that the performance of rollable roadway systems under tyred vehicle trafficking will be improved by eliminating joint rotation to increase longitudinal stiffness.

Loading configuration effects on the strength reliability of alumina–zirconia multilayered ceramics

The loading configuration effects on the strength reliability of alumina/zirconia multilayered systems, designed with internal compressive stresses, have been investigated. The existence of a threshold strength behaviour, as previously assessed under longitudinal flexure, has been evaluated by indentation-strength tests under transverse flexure. Additionally, the influence of flaw interactions on the strength reliability under both loading configurations has also been studied. Experimental findings show a higher strength level under transverse flexure, as far as the failure-controlling flaw is located between two compressive layers. It is found however that multiple artificial and natural flaws may interact affecting the strength of the specimen under transverse loading. As a consequence, although higher strength values result from this configuration, a more reliable design is rather attained when the loading axis is applied normal to the layer plane, a loading mode where similar effects are negligible.