Specific Local Resistance Research Articles

A state-of-the-art review of progressive collapse research and guidelines for single-layer lattice shell structures

The importance of progressive collapse analysis of structures has increased significantly due to various structural collapses. Single-layer lattice shell structures are susceptible to progressive collapse, as the failure or instability of a localised region can result in a global collapse due to their lightness and wide span. The geometry of these structures plays a crucial role in the load resistance, and any damage that alters the overall geometry can initiate different instabilities, which may also result in progressive collapse. Therefore, the possibility of progressive collapse is high among these lighter structural forms. However, research on the progressive collapse of single-layer lattice shell structures is limited compared to framed structures, highlighting the need for further investigation. Therefore, this manuscript aims to provide a comprehensive review of research conducted on the progressive collapse of single-layer lattice shell structures, focusing on experimental, numerical, and theoretical investigations. Earlier studies have explored the propagation of local instabilities leading to overall failure. More recent research has primarily focused on two approaches: (1) alternate path analysis, which examines the structure’s response after removing a member, and (2) substructure analysis, which aims to identify collapse-preventive mechanisms. Based on these analyses, various methods to enhance progressive collapse resistance have been discussed, including specific local resistance, alternate load paths, compartmentalisation, and tie forces. This review also highlights the limitations present in the current literature and suggests future research directions, which helps to develop design guidelines that can effectively increase the progressive collapse resistance of single-layer lattice shell structures, making them more reliable for various structural applications.

Suppurative lymphadenitis

Suppurative lymphadenitis is an important and common form of soft tissue infection. Most acute cases of suppurative lymphadenitis are caused by Staphylococcus aureus or by Streptococcus pyogenes. Empiric antibiotic therapy is frequently successful in the early stages of the disease process, but increasing prevalence of methicillin-resistant S. aureus in particular has necessitated a shift in antibiotic choice that is dictated primarily by specific local resistance patterns. Several other organisms and noninfectious inflammatory processes may give rise to a clinical syndrome suggestive of suppurative lymphadenitis. Failure to respond to empiric antibiotics should trigger a diagnostic re-evaluation to determine the need for surgical intervention and/or the possibility of alternative microbiologic diagnoses.

Avoiding Disproportionate Collapse of Tall Buildings

Accidental circumstances must not result in disproportionate collapse. Strategies for achieving this goal are studied and corresponding design concepts are developed. The focus is on large and slender buildings with a high degree of significance and exposure. The study is based on an examination, one by one, of five general approaches: nonstructural protective measures, specific local resistance, alternative paths, isolation of collapsing sections, and prescriptive design rules. Departing from the specific-local-resistance approach, an arrangement of independent primary and secondary load transfer systems is arrived at where the primary system consists of a compact reinforced-concrete tube forming the vertical spine of the building. Based on the isolation approach, a vertical segmentation accomplished by strengthened floor slabs is suggested where a commencing pancake-type collapse is arrested by dissipating energy in shock-absorbing devices. These two design concepts maximize the tolerable accidental circumstances. The alternative-paths approach can be used for secondary systems or when a set of limited accidental actions is agreed upon.

Disproportionate collapse: a pragmatic approach

Probability-based design methods face certain problems in making structures sufficiently collapse resistant and thus preventing disproportionate collapse. These problems are addressed and a discussion is given to outline how they might be overcome both within and outside a probabilistic framework. Definitions for the terms ‘robustness’ and ‘collapse resistance’ are proposed, the former being a property of the structure alone, the latter including possible causes of initial local failure. A pragmatic approach for designing against disproportionate collapse is suggested and a set of corresponding design criteria is presented. Design strategies based on preventing or presuming local failure are compared. In addition to the better-known design methods providing specific local resistance or alternative paths, an approach based on isolation by segmentation is examined. It is found that the applicability of the various design methods depends on the design objectives and on the type of structure.

Incorporation of endogenous prolactin by granulosa cells and dictyate oocytes in the postpartum rat: effects of estrogen.

Ovarian follicles were examined for the presence and distribution of endogenous PRL in nor mally lactating control rats and comparable rats which had been subjected no a variety of annilacta tional, luteonropic estrogen treatments. Control ovaries contained both preantral follicles and annral follicles up to 500 @m in diameter. In healthy antral follicles, PRL was present in the cyno plasm and nuclei of granulosa cells (GC), in follicular fluid (FF) and also in the cytoplasm of the manuring dicnyane oocynes (OC), where ins lattice-like distribution resembled that of, and sug gesned an association with, yolk material. PRL was distributed similarly in OC of healthy preannral follicles, but in was absent from the surrounding GC. In anresia, both GC and OC showed disturb ances of PRL distribution (absence from GC nuclei, irregular staining of yolk lattice) or complete absence of staining for PRL. The changes in OC were seen in rats given only 4 @g estradiol benzo ate/day. Stronger estrogen treatments produced anrenicchanges in GC as well. These findings suggest at least two periods of PRL incorporation by healthy dicnyane OC: one prior no, or early in, the stage of meionic arrest, the other during preovulanory manuranional en largement. During the later period, when PRL is transported no the OC through GC cytoplasm and FF, in also enters GC nuclei. The prolonged retention of PRL within the OC and ins renewed in corporation as this cell approaches innerphase, together with recent evidence that PRL may play a role in the inhibition of meiosis in mammalian oocynes, suggest that the specific local resistance no ovulation -inducing stimuli, which is needed for both selective maintenance of the dicnyane state and fine control of preovulatory maturation, might be a function of the PRL snored within the OC itself.

TREATMENT OF OCULAR TUBERCULOSIS

The results of treatment with tuberculin in 42 cases of ocular tuberculosis in the Wilmer Ophthalmological Institute were analyzed and reported in 1928. 1 The statement was then made that the manner in which tuberculin acted, whether as a specific desensitizing agent or by augmenting the specific local resistance by a succession of small stimuli, was not known. Since this report our knowledge of the influence of allergy and immunity on tuberculous lesions has been considerably clarified. We have therefore reviewed the cases of all patients with ocular tuberculosis treated with tuberculin or by other procedures in the public wards or in private practice in the Wilmer Ophthalmological Institute and have analyzed these cases in the light of this newer knowledge of tuberculosis. The study is the subject of this report. The influence of allergy and immunity on local tuberculous lesions has already been discussed by one of