True Tear Research Articles

Diametral compression of short cylinders with a central hole as a method for assessing the tear resistance of brittle materials

The possibility of evaluating the tear resistance of brittle materials by diametral compression test of short cylinders (solid and central with a central hole) has been analyzed. The computational analysis was performed by the finite element method using the ANSYS program. It is shown that the stress distribution in a disk with a hole is similar that without a hole but contains disturbances introduced by a stress concentrator in the form of a hole. The normalized values of the maximum first principal stresses for a disk with a hole exceed the values for a disk without a hole by more than 5 times. The experimental analysis was carried out by testing short cylinders, both solid and with a central hole, made of brittle materials: cast iron and graphite. It is noted that the fracture resistance, determined by the formula recommended by the ASTM D3967 – 95a standard, practically does not differ for solid cast iron samples, and for graphite differs by 1.5 times from the true tear resistance of materials; when testing samples with a central hole, the tear resistance differs from the standard values by a factor of 1.5 and almost 2.5, respectively. The different nature of the sample destruction is also noted: slow controlled rupture of cast iron and dynamic destruction of graphite with the corresponding deformation diagrams. The results of testing fuel pellets of uranium dioxide are given as an example of testing real cylindrical samples with a central hole. It is shown that the test results of ARV-1 graphite samples are in good agreement with the test results of fuel samples. Thus, the possibility of testing small-sized short cylinders according to the diametral compression scheme for indirect assessment of the tensile strength of brittle materials has been confirmed. A calculation formula is proposed for an indirect assessment of the tensile strength of brittle materials based on the results of testing small-sized short cylinders, both with and without a central hole according to the diametral compression scheme.

Arthroscopic Bennett Lesion Resection: A Novel Technique

Background: Bennett lesion is ossification of the posterior inferior glenohumeral ligament complex. Though often asymptomatic, these lesions can become painful and interfere with throwing ability. Indications: The Bennett lesion is relatively common among elite throwers, present in 22% to 25% of asymptomatic pitchers. Suggested causes of this lesion include traction on the posterior joint and posterior impingement in the late cocking phase. These lesions can become painful due to displacement and irritation of the joint capsule and axillary nerve. Therefore, efficient arthroscopic treatment of symptomatic lesions is essential. Technique Description: The patient is positioned in the lateral decubitus position, and the glenohumeral joint is accessed via posterior and anterior portals. Once the lesion is identified, it may be probed and debrided via the posterior portal. A posterior capsular release is performed, and 4.0 mm burr resection of the lesion is started, viewing from the anterior portal with a 70° arthroscope. Direct visualization through the posterior portal can be used to verify complete lesion resection. If there is a true tear of the posterior labrum, this can be repaired with a knotless suture anchor back to the glenoid, but usually there is delamination that can be left alone after addressing the Bennett lesion. Results: We have found good success treating Bennett lesions via the above technique. This is supported by previous literature as well, with return to preinjury levels ranging from 69% to 85% following arthroscopic resection. Discussion/Conclusion: Four diagnostic criteria have been described to ensure accurate diagnosis: detection of a bony spur at the posterior glenoid rim on plain x-ray films, best seen on Stryker notch and Bennett view; posterior shoulder pain while throwing; tenderness at the posteroinferior aspect of the glenohumeral joint; and improvement in pain following lidocaine injection. Magnetic resonance imaging is also an excellent diagnostic tool to detect early enthesopathic changes in the posterior glenoid or periosteum, as well as labral pathology. Following arthroscopic resection, 88% of patients were satisfied with their treatment when using these diagnostic criteria. Accurate diagnosis and efficient treatment of Bennett lesions are imperative in the throwing athlete, and when performed correctly, our technique provides significant and lasting improvement for patients.

한석원(韓錫源) 목사의 ‘낙루신앙’(落淚信仰) 소고 : 그의 “眞情의 淚”(1921)를 중심으로

이 연구의 목적은 한석원(韓錫源) 목사의 “眞情의 淚”(1921)를 통해 ‘낙루신앙’(落 淚信仰)에 대한 그의 담론을 고찰하는 데 둔다. 그는 누가복음 19장 41절과 42절을 본문으로 설정하여 이 글을 저술했다. “가까이 오사 성을 보시고 우시며 이르시되 너 도 오늘 평화에 관한 일을 알았더라면 좋을 뻔하였거니와 지금 네 눈에 숨겨졌도다.” 한석원의 낙루신앙에 관한 중요한 관점은 그의 희귀본 옥고 “眞情의 淚”에서 살펴볼 수 있고, 이 글은 일제강점기 1921년 9월에 출간된 『百牧講演(第一集)』에 수록되어 있다. 이 책은 당대 기독교계의 명성 있는 한국인 지도자 22인과 선교사 3인의 진귀 한 설교문들을 집록한 문헌이다. 한석원의 글 “眞情의 淚”에 나타난 핵심적인 논점들과 주요사안들은 다음과 같다. 첫째, 한석원의 눈물의 속성에 관한 관점과 관련하여 감사, 동정, 애정, 결별, 간청, 회한의 눈물에 대해 설명했다. 둘째, 예수 그리스도의 눈물과 관련된 의미심장한 논점들로서 애련(요한복음 11:33), 비애(누가복음 19:41-42), 피땀(누가복음 22:44) 등 삼중적 의미에 대하여 초점 을 맞추었다. 셋째, 한석원의 신앙과 내면적 고백에 기초하여 한국 그리스도인들에게 당부한 간 곡한 호소를 살펴보았다. 그는 한국 그리스도인들에게 한국의 미래를 위해 힘써 기도 할 것, 순교정신과 이타정신을 갖출 것을 촉구했다. 한석원 목사가 남긴 의미 있는 발자취와 한국교회를 향한 주목할 만한 헌신에 비 추어 본 연구자는 앞으로 그와 관련된 담론을 외연(外延)함으로써 본 주제 외에도 기 독교 서적 편찬과 발행, 주일학교 교육업적, 기독교 신앙의 관점, 기독교서적 보급, 청 년운동 목회 등 여러 방면의 담론으로 확장되기를 기대해본다.

MR Arthrogram Features That Can Be Used to Distinguish Between True Inferior Glenohumeral Ligament Complex Tears and Iatrogenic Extravasation.

The purpose of this study is to identify features seen at shoulder MR arthrography that distinguish between iatrogenic contrast material extravasation and inferior glenohumeral ligament (IGHL) complex tears. MR arthrograms (n = 1740) were screened for extravasation through the IGHL complex. Cases were defined on the basis of surgical findings or definitive lack of extravasation in a fully distended joint immediately after contrast agent injection. The location of the disruption and the morphologic features of the torn margin were assessed and compared between groups. Anterior band disruption was present in eight of 16 patients with true tears and in zero of 19 patients with iatrogenic contrast material extravasation (p < 0.001). Isolated extravasation through the posterior half of the axillary pouch was present in 12 patients with iatrogenic extravasation, compared with none of the patients with true tears (p < 0.001). Thick ends were present in 10 of the true tears, whereas none of the cases of iatrogenic extravasation showed this finding (p < 0.001). Scarred margins were seen in eight true tears and none of the iatrogenic extravasation cases (p < 0.001). The presence of a torn anterior band, thick ligament, reverse-tapered caliber, and scarred appearance of the torn margin were shown to be 100.0% specific, and a torn posterior band showed 84.2% specificity for true tears. The presence of isolated involvement of the posterior portion of axillary pouch showed 63.2% sensitivity and 100.0% specificity for iatrogenic extravasation. A torn anterior band, a thickened ligament (> 3 mm), reverse-tapered caliber, and scarred margin were 100.0% specific for a tear. Isolated disruption of the posterior axillary pouch was 100.0% specific for iatrogenic extravasation.

Tear exchange and contact lenses: A review

Tear exchange beneath a contact lens facilitates ongoing fluid replenishment between the ocular surface and the lens. This exchange is considerably lower during the wear of soft lenses compared with rigid lenses. As a result, the accumulation of tear film debris and metabolic by-products between the cornea and a soft contact lens increases, potentially leading to complications. Lens design innovations have been proposed, but no substantial improvement in soft lens tear exchange has been reported. Researchers have determined post-lens tear exchange using several methods, notably fluorophotometry. However, due to technological limitations, little remains known about tear hydrodynamics around the lens and, to-date, true tear exchange with contact lenses has not been shown. Further knowledge regarding tear exchange could be vital in aiding better contact lens design, with the prospect of alleviating certain adverse ocular responses.This article reviews the literature to-date on the significance, implications and measurement of tear exchange with contact lenses.

Les ruptures du tendon du muscle tibial antérieur

In sports medicine, tears of the tibialis anterior are exceptional. We describe our experience with one case. Two types of injury can be observed: true tears involving the main body of the muscle under the pulley or the more distal portion at the insertion and fissurations. These injuries usually occur in a context of longstanding tenosynovitis or tendinopathy and are generally observed in runners. The mechanism requires stretching with the foot in forced plantar flexion and external rotation (fall backward with forefoot blocked). The diagnosis is clinical. Complementary explorations, excepting plain X-rays to search for a distal detachment from the bone, are not indispensable. In sports medicine, surgical treatment is required for full thickness tears. A plasty is usually performed with the third toe extensor. Recovery is long and progressive. In our experience, corticosteroid injections do not provoke these tears but can be useful for more rapid recovery in the athlete. After an injection, we immobilize the ankle for three weeks in a walking cast in order to “limit” the motivated athlete.

New interpretations of the Piney Creek thrust and associated Granite Ridge tear fault, northeastern Bighorn Mountains, Wyoming

The northwest-striking, northeast-directed Piney Creek thrust on the northeastern flank of the Bighorn Mountains in north-central Wyoming is traditionally interpreted as abruptly terminated on the northwest by the transverse Granite Ridge fault zone (new name). The structure of the mountain front north of this fault generally has been described as an unfaulted monocline. However, seismic-reflection, gravity, and borehole data, and the requirement of reasonable shortening balance along the mountain front indicate subsurface continuity of the (buried) Piney Creek thrust northward from the Granite Ridge fault zone—perhaps to the Tongue River lineament near the Montana border. Based on these subsurface data, the Granite Ridge fault is described here as a true tear fault confined to the hanging wall of an uninterrupted, ∼30°-dipping Piney Creek thrust, segmenting hanging-wall thrust displacement between the Piney Creek block on the south and Walker Mountain block on the north. Slip on the Granite Ridge tear fault is expressed at the surface along the eastern margin of the Bighorn Mountains, west of Story, Wyoming, as a resequent fault-line scarp with ∼2000 ft (600 m) of relief, and with ∼3.3 mi (∼5.3 km) of left separation of steeply dipping, Paleozoic rocks. Based on measurement between piercing points produced by the lines of intersection of the steeply, east-dipping Cambrian-Precambrian unconformity with the Piney Creek thrust surface along either side of the Granite Ridge tear fault, a (reverse) left-oblique slip of ∼15,000 ft (∼4500 m) is measured on this tear fault zone. Thus, 30,000 ft (9100 m) of net slip on the Piney Creek thrust in the Piney Creek block decreases to 15,000 ft (4500 m) of net slip in the Walker Mountain block, and slip on the thrust further declines northward. The described Granite Ridge tear fault–Piney Creek thrust geometry may provide a useful model in the investigation of similar fault-offset mountain fronts within the Laramide foreland province of the Middle Rocky Mountains.

Pitfalls in knee arthrography.

Sources of error in performing and interpreting knee arthrograms are discussed. Normal anatomic structures and technical factors can simulate tears in most areas of both the medial and lateral menisci. These pseudotears, as well as unrecognized true tears, occur more commonly in the posterior horn of the medial meniscus. Inferior meniscal recesses and coronary ligament irregularities of the posterior medial meniscus often represent incomplete tears. Diagnostic, etiologic, and therapeutic aspects of these recesses, or pseudorecesses, are discussed. Excessive intra-articular positive contrast medium may become localized and simulate a loose body in the joint.

The Tear Strength of Vulcanizates

Abstract 1) The force acting upon the jaws of the tear testing machine is always measured in tear strength tests and its value serves as a criterion of the tear resistance. This force, measured at the instant of completion of the tear, is made up of the force necessary for tear propagation in the notch together with the force needed to produce the elongation of the material in the notched cross section. The proportion of these two components is quite different, depending on the form of the testpiece. The effort should be made to attain the highest possible stress concentration in the notch with the lowest possible elongation in the rest of the testpiece, so that the force that operates on the jaws will represent chiefly the force needed for tearing. 2) Two principle groups of testpieces are to be distinguished: those which show a tear propagation rate determined by the speed of the jaws and those with spontaneous tear propagation. 3) For the case of a thin cut with a razor blade in the testpiece, the tear which occurs upon stretching should not be thought of as a tear growth of the cut, but is to be regarded as a new tear initiation. 4) Several pieces of equipment with electronic force measuring instruments were devised to study the effect of jaw speed. The measurements were performed at jaw speeds up to 18 m/sec. 5) The tensile strengths of the vulcanizates which were studied fall off at first with increase in speed and then rise at high speeds. 6) The curve for tear strength as a function of speeds is similar to that for tensile strength. After passing through a minimum, the tear strengths of the vulcanizates generally rise for the higher speeds. 7) This increase in tear strength was especially large for the synthetic polymers studied. At a test speed of 18 m/sec, their tear strengths reached values several times larger than for lower speeds. 8) An explanation of the changes in tensile strength and tear strength with speed and temperature may be found in orientation and crystallization at high elongation on the one hand and in the flow processes on the other. 9) Changes in relative ratings appear when we compare the results of tear strength measurements on various vulcanizates because the testing speed affects them to different extents. 10) The material becomes anisotropic because of varying high local elongation and the accompanying orientation in the tear test specimen, and the resistance to tear propagation becomes dependent upon direction. The ruptured surfaces of the sample as well as the force/time diagram frequently show a saw-tooth character (“knotty tear”). Smooth or knotty tear occurs for every compound depending upon the testing conditions. 11) The ordinary tear strength test is, therefore, a test of structural strength, which is made up of the true tear propagation load, needed for the tearing, together with the load required for the deformation of the legs between jaws. Test speed and temperature exert different effects on each of these components. From what has been said, it follows that in the use of a given article, it is necessary that we give careful consideration to the sevice conditions, and hence we are not yet in a position to make a generally applicable recommendation for the form of the test specimen.