Vibration analysis of a printed circuit board

The reliability of the printed circuit board assembly under dynamic environments, such as those found onboard airplanes, ships and land vehicles is receiving more attention. This research analyses the dynamic characteristics of the printed circuit board (PCB) supported by edge retainers and plug-in connectors. By modelling the wedge retainer and connector as providing simply supported boundary condition with appropriate rotational spring stiffnesses along their respective edges with the aid of finite element codes, accurate natural frequencies for the board against experimental natural frequencies are obtained. For a PCB supported by two opposite wedge retainers and a plug-in connector and with its remaining edge free of any restraint, it is found that these real supports behave somewhere between the simply supported and clamped boundary conditions and provide a percentage fixity of 39.5% more than the classical simply supported case. By using an eigensensitivity method, the rotational stiffnesses representing the boundary supports of the PCB can be updated effectively and is capable of representing the dynamics of the PCB accurately. The result shows that the percentage error in the fundamental frequency of the PCB finite element model is substantially reduced from 22.3% to 1.3%. The procedure demonstrated the effectiveness of using only the vibration test frequencies as reference data when the mode shapes of the original untuned model are almost identical to the referenced modes/experimental data. When using only modal frequencies in model improvement, the analysis is very much simplified. Furthermore, the time taken to obtain the experimental data will be substantially reduced as the experimental mode shapes are not required.In addition, this thesis advocates a relatively simple method in determining the support locations for maximising the fundamental frequency of vibrating structures. The technique is simple and does not require any optimisation or sequential search algorithm in the analysis. The key to the procedure is to position the necessary supports at positions so as to eliminate the lower modes from the original configuration. This is accomplished by introducing point supports along the nodal lines of the highest possible mode from the original configuration, so that all the other lower modes are eliminated by the introduction of the new or extra supports to the structure. It also proposes inspecting the average driving point residues along the nodal lines of vibrating plates to find the optimal locations of the supports. Numerical examples are provided to demonstrate its validity. By applying to the PCB supported on its three sides by two wedge retainers and a connector, it is found that a single point constraint that would yield maximum fundamental frequency is located at the mid-point of the nodal line, namely, node 39. This point support has the effect of increasing the structure's fundamental frequency from 68.4 Hz to 146.9 Hz, or 115% higher.

Current Status of Collectibility of Gaming-Related Credit Dollars

In her piece entitled - Current Status Of Collectability Of Gaming-Related Credit Dollars - Ruth Lisa Wenof, Graduate Student at Florida International University initially states: “Credit is an important part of incentives used to lure gamblers to gaming establishments. However, a collection problem exists in casinos retrieving gaming-related credit losses of individuals living in states where gambling is illegal. The author discusses the history of this question, citing recent cases related to Atlantic City.” This author’s article is substantially laden with legal cases associated with casinos in New Jersey; Atlantic City to be exact. The piece is specific to the segment of the gaming industry that the title suggests, and as such is written in a decidedly technical style. “Legalized casino gaming, which was approved by the citizens of New Jersey on November 8, 1976, has been used as a unique tool of urban redevelopment for Atlantic City,” Wenof says in providing some background on this ‘Jersey shore municipality. “Since Resorts International opened its casino…revenues from gambling have increased rapidly. Resorts' gross win in 1978 was $134 million,” Wenof says. “Since then, the combined gross win of the city's 11 casinos has been just shy of $7.5 billion.” The author points out that the competition for casino business is fierce and that credit dollars play an integral role in soliciting such business. “Credit plays a most important part in every casino hotel. This type of gambler is given every incentive to come to a particular hotel,” says the author. “Airplanes, limousines, suites, free meals, and beverages all become a package for the person who can sign a marker. The credit department of a casino is similar to that of a bank. A banker who loans money knows that it must be paid back or his bank will fail. This is indeed true of a casino,” Wenof warns in outlining the potential problem that this article is fundamentally designed around. In providing further background on credit essentials and possible pitfalls, Wenof affords: “…on the Casino Control Act the State Commission of Investigation recommended to the legislature that casinos should not be allowed to extend credit at all, by reason of a concern for illicit diversion of revenues, which is popularly called skimming within the industry…” Although skimming is an after-the-fact problem, and is parenthetic to loan returns, it is an important element of the collective [sic] credit scheme. “A collection problem of prime importance is if a casino can get back gaming-related credit dollars advanced by the casino to a gambler who lives in a state where gambling is illegal,” is a central factor to consider, Wenof reveals. This is a primary focus of this article. Wenof touches on the social/societal implications of gambling, and then continues the discussion by citing a host of legal cases pertaining to debt collection.

Women at work: flight engineer.

Inscription: Verso: Women at work: miscellaneous occupations. Julia B. Canter, United Airlines, flight engineer.

Gravity collapse structures in the Central Precordillera fold-andthrust belt, Argentina

Several landforms found in the fold-and-thrust belt area of Central Precordillera, Pre-Andes of Argentina, which were often associated with tectonic efforts, are in fact related to non-tectonic processes or gravitational superficial structures. These second-order structures, interpreted as gravitational collapse structures, have developed in the western flank of sierras de La Dehesa and Talacasto. These include rock-slides, rock falls, wrinkle folds, slip sheets and flaps, among others; which together constitute a monoclinal fold dipping between 30º and 60º to the west. Gravity collapse structures are parallel to the regional strike of the Sierra de la Dehesa and are placed in Ordovician limestones and dolomites. Their sloping towards the west, the presence of bed planes, fractures and joints; and the lithology (limestone interbedded with incompetent argillaceous banks) would have favored their occurrence. Movement of the detached structures has been controlled by lithology characteristics, as well as by bedding and joints. Detachment and initial transport of gravity collapse structures and rockslides in the western flank of the Sierra de la Dehesa were tightly controlled by three structural elements: 1) sliding surfaces developed on parallel bedded strata when dipping >30° in the slope direction; 2) Joint’s sets constitute lateral and transverse traction cracks which release extensional stresses and 3) Discontinuities fragmenting sliding surfaces.  Some other factors that could be characterized as local (lithology, structure and topography) and as regional (high seismic activity and possibly wetter conditions during the postglacial period) were determining in favoring the steady loss of the western mountain side in the easternmost foothills of Central Precordillera.

The Hall-Findlay mammaplasty pattern for skin-sparing mastectomy. Case report

We present an application of the Hall-Findlay mammaplasty skin pattern for skin-sparing mastectomy (SSM). This is a simplified vertical reduction mammaplasty. Vertical reduction mammaplasty is the procedure advised for patients with moderator or large ptotic breasts, who wish to have a simultaneous contra-lateral breast reduction/mastopexy at the time of SSM for cancer or prophylactic mastectomy. It is particularly suitable for breast reconstruction with autologous tissue in the form of free transverse rectus abdominis myocutaneous (TRAM), deep inferior epigastric artery perforator (DIEP) and extended latissimus dorsi (ELD) flaps.

Alveolite

A etiologia da alveolite é desconhecida. Considera-se não haver uma causa específica, mas sim uma associação de factores inerentes ao seu aparecimento. O diagnóstico é realizado, geralmente, entre o 2º e 5º dia após exodontia, sendo bastante claro. Manifesta-se por uma dor aguda e pulsátil, mal controlada com analgésicos, e de apresentação clínica uma inflamação da mucosa em torno do alvéolo, com parcial ou total perda do coágulo, apresentando-se este vazio ou com tecido necrótico e/ou restos alimentares. Pode ainda haver uma exposição óssea. Diversas são as taxas de incidência, variando consoante os factores de risco predisponentes da doença. São estes a idade, género, ciclo menstrual e toma de contraceptivos orais (nas mulheres), trauma cirúrgico e experiência do médico, a indicação da extração, bem como características do dente a ser extraído, ainda as técnicas e anestesia usadas, bem como remanescentes ósseos e/ou radiculares, uso de retalhos e suturas, patologias sistémicas, medicação e cuidados pós-operatórios do doente. Todos estes podem ter impacto no desenvolvimento desta condição, devendo o médico dentista eliminá-los e reduzi-los ao máximo. A prevenção aplica-se a medidas não farmacológicas, como redução de factores de risco, em combinação a terapia farmacológica, de modo a favorecer uma correta cicatrização. Recurso a soluções antissépticas, medicação tópica (intra-alveolar) e prescrição sistémica de antibióticos e anti-inflamatórios não esteroides são algumas dessas medidas. Ao nível do tratamento, vários métodos e materiais estão disponíveis no mercado. Por ser uma condição que o próprio organismo “combate”, o objectivo terapêutico passa basicamente pela redução dos sintomas debilitantes do paciente e controlo bacteriano. A opção é individual, uma vez que não existe nenhum tratamento com características ideais, sendo os resultados na literatura bastante discrepantes. Limpeza do alvéolo, medicação intra-alveolar (tópica) e/ou sistémica, bem como terapia com laser de baixa intensidade, são algumas opções. A administração antibiótica deve ser reservada para casos especiais, não devendo ser abordada como método de rotina. Analgésicos são uma opção, podendo ser aconselhada consoante o quadro clínico doloroso. Também o reforço para uma higiene oral rigorosa, com irrigação do alvéolo para evitar detritos e impactação alimentar (no caso de não existirem obtundantes intra-alveolares) devem ser preocupação do médico dentista. Deve haver um seguimento regular do paciente, especialmente se aplicados medicamentos tópicos, para avaliação e renovação (se necessário) do curativo até recuperação. O médico dentista deve saber identificar um caso de alveolite, encontrando-se informado e consciente das várias opções preventivas e terapêuticas. Estudos mais claros e objectivos são necessários na procura de critérios de diagnóstico genéricos da doença, bem como terapêuticas preventivas e de tratamentos com taxas de sucesso altas e suportadas por evidência científica. Para que, desta forma, seja elaborado um protocolo universal a seguir na prática clínica.

Prevenção da reabsorção óssea alveolar após extração dentária

Introdução: O processo alveolar é o conjunto de osso que se encontra em redor da raiz do dente. Este osso é sensível a uma variedade de fatores ambientais e fisiológicos que influenciam a sua integridade e o seu funcionamento. Como tal, a sua formação assim como a sua preservação é dependente da presença contínua do dente. A reabsorção do processo alveolar após extração dentária é uma consequência natural e fisiológica indesejável, que pode dificultar a colocação de um implante dentário na posição desejada. Com o aumento cada vez mais das demandas estéticas em medicina dentária, torna-se, portanto, necessário prevenir que a reabsorção óssea provoque este defeito na arcada dentária. Objetivos: Realizar uma revisão bibliográfica sobre as várias técnicas e materiais para preservação do rebordo alveolar, a fim de prevenir ou minimizar a reabsorção alveolar após extração dentária. Material e Métodos: A pesquisa foi realizada nas bases de dados Pubmed, B-on e Scielo, não foi aplicado nenhum limite temporal, e os critérios de inclusão foram artigos em língua inglesa e portuguesa. Num total de 164 artigos, selecionaram-se 82 estritamente relacionados com o tema. Os artigos excluídos desviavam-se do objetivo do trabalho ou eram inconclusivos. Selecionaram-se, também, capítulos do livro Clinical Periodontology and Implant Dentistry Volume 1 e 2, dos autores Niklaus P.Lang e Jan Lindhe. Desenvolvimento: De modo a compreender como o processo alveolar reabsorve, deve-se ter em conta as várias técnicas que se podem realizar para permitir uma boa quantidade de osso remanescente na arcada adequada a cada caso para uma possível reabilitação. As técnicas de preservação do osso alveolar após extração passam pela realização de técnicas cirúrgicas minimamente invasivas, estabilização do coágulo pelo princípio da cicatrização por primeira intenção usando membranas ou retalhos, preenchimento do alvéolo dentário com materiais de enxerto ou substitutos ósseos, terapias combinadas com a colocação de implantes imediatos e o recurso a células e fatores de crescimento. Conclusão: A preservação alveolar tem grande importância para uma posterior reabilitação oral com implantes com maior quantidade de osso disponível do que quando não é feita qualquer tipo de preservação. A extração das peças dentárias deve ser feita com cuidado para preservar ao máximo ou não danificar as superfícies ósseas remanescentes. É aconselhado que o encerramento da ferida seja por primeira intenção e que proporcione estabilidade ao coágulo, podendo ser usado retalhos ou mesmo membranas. O uso de enxertos ósseos tem uma importante função de proporcionar uma matriz para o coágulo se formar e promover o processo de cicatrização. O método de implante imediato, para além de ser bastante usado, tem como finalidade o conforto para o paciente de não ser submetido a uma posterior cirurgia para colocação do mesmo e, simultaneamente, mantem a estabilidade dos tecidos moles. Ainda uma técnica menos usada é com células e fatores de crescimento que proporciona uma cicatrização mais rápida e um aumento do potencial regenerativo dos tecidos.

Improving the assessment and outcome of free tissue transfer breast reconstruction

Introduction: Free tissue transfer using an abdominal tissue flap is a commonly used method of breast reconstruction. However, there are well recognised complications including venous congestion, fat necrosis and flap loss associated with the perfusion of these flaps. Post-operative aesthetic outcome assessment of such breast reconstructions have also proven to be difficult with current methods displaying poor inter-rater reliability and patient correlation. The aim of this research was to investigate potential improvements to the post-operative outcome of free abdominal tissue transfer breast reconstruction by assessing the effects of vascular augmentation interventions on flap perfusion and to assess the use of real-time digital video as a post-operative assessment tool. Methods: An in-vivo pilot study carried out on 12 patients undergoing DIEP flap breast reconstruction assessed the effect on Zone IV perfusion, using LDI and ICG angiography, of vascular augmentation of the flap using the contralateral SIEA and SIEV. A further animal experimental study was carried out on 12 Sprague Dawley rats to assess the effects on main pedicle arterial blood flow and on Zone I and Zone IV perfusion of vascular augmentation of the abdominal flap using the contralateral vascular system. A separate post-operative assessment study was undertaken on 35 breast reconstruction patients who evaluated their own reconstructions via patient questionnaire and underwent photograph and real-time digital video capture of their reconstructions with subsequent panel assessment. Results: Our results showed that combined vascular augmentation of DIEP flaps, using both the SIEA and SIEV together, led to an increase in Zone IV perfusion. Vascular augmentation of the rat abdominal flaps also led to a significant increase in Zone I/IV perfusion, but the augmentation procedure resulted in a decreased main pedicle arterial blood flow. Our post-operative assessment study revealed that real-time digital video footage led to greater inter-rater agreement with regards to cosmesis and shape than photography and also correlated more with patient self-assessment. Conclusion: Vascular augmentation of abdominal free tissue flaps using the contralateral vascular system results in an increase to Zone IV perfusion, however this may lead to decreased main pedicle arterial blood flow. Real-time digital video is a valid post-operative aesthetic assessment method of breast reconstruction outcome and is superior to static photography when coupled with panel assessment.

The natural pilot model for flight proficiency evaluation

Cover title.

Flight tests of the ramjet on aircraft designed by N. N. Polikarpov in 1939-1940

Photocopied from an unknown journal or work.

Approximate solutions to optimum flight trajectories for a turbo-jet powered aircraft,

"Purdue Research Foundation. Research project no. 1255. Project Ae-25. This research was supported by the National Advisory Committee for Aeronautics, Washington, D. C., under Contract no. NAW-6465."

Variable stability research aircraft. Submitted to the Panel on Acceleration Stress of the Armed Forces, National Research Council Committee on Bio-Astronautics, Woods Hole Conference, 16-24 July, 1959.

Cover title.

Effects of aluminum on cells and tissues

International audience

Evaluation of hemosponge in promoting dental socket healing after 3rd mandibular premolar extraction in a feline model

Aim: To investigate the healing process following use of collagen sponges in the dental socket after extraction. Wound complications during the study were also evaluated. Methods: 32 cats were included in this study. IV administration of the combination of diazepam (0.22 mg/kg) and ketamine (10 mg/kg) was used to induce general anesthesia. Surgical extraction of both 3rd mandibular premolars was performed. The open dental sockets were divided in two groups. In Group A, the open dental socket on the left side was closed using 4-0 Monocryl in simple interrupted pattern. In Group B, the right dental socket was filled with lyophilized hydrolyzed collagen and the buccal and lingual flaps were sutured using 4-0 Monocryl and simple interrupted pattern. Meloxicam (0.2 mg/kg) was used to manage the post-extraction pain in all cats. Ampicilline 20 mg/kg was used as prophylaxis. The wounds were observed during the study to evaluate any signs of inflammation or dehiscence. Radiographs were taken to compare healing of the socket 3 weeks after the procedure. A 1 mm biopsy punch sample was taken from sockets in all cats for comparison of the healing in both groups. Results: Hemorrhage occurred only in the sockets of Group A. Remission of radiolucent area occurred in both groups. Mean score of inflammation was lower and mean scores of fibrotic reaction and fibroplasia were higher in Group B (p<0.05). Conclusions: Use of hemosponge in alveolar socket may accelerate fibroplasia and formation of the connective tissue and reduce inflammation after tooth extraction. Therefore, post-extraction use of the hemostatic agent in the dental socket is recommended.