bluuebunny/crossref_metadata_2025 huggingface dataset:
German neuroendoscopy above the skull base
Authors: Grunert Peter , Gaab Michael R. , Hellwig Dieter , Oertel Joachim M. K.
Published: September 2009

Endoscopy plays an important part in current minimally invasive neurosurgery. The concepts, indications, and standards of current neuroendoscopy were developed in the beginning of the 1990s by several groups of neurosurgeons. Several factors contributed to its success and acceptance, including technical development, influence of other disciplines, and adaptation to neurosurgical requirements. This historical survey focuses on the period when this technique initially emerged, including the scientific discussions of each group as well as the arguments and reasons that led to present intraventricular neuroendoscopy. Interestingly, despite the almost independent development of neuroendoscopic systems and techniques, the available systems and techniques applied these days grossly correspond. Rigid rod-lens endoscopes are generally accepted as the best option among the various available instrument sets. Nevertheless, frameless as well as frame-based stereotactic endoscopy and flexible steerable endoscopes might have their applications as well.
Aura of technology and the cutting edge: a history of lasers in neurosurgery
Authors: Ryan Robert W. , Spetzler Robert F. , Preul Mark C.
Published: September 2009

In this historical review the authors examine the important developments that have led to the availability of laser energy to neurosurgeons as a unique and sometimes invaluable tool. They review the physical science behind the function of lasers, as well as how and when various lasers based on different lasing mediums were discovered. They also follow the close association between advances in laser technology and their application in biomedicine, from early laboratory experiments to the first clinical experiences. Because opinions on the appropriate role of lasers in neurosurgery vary widely, the historical basis for some of these views is explored. Initial enthusiasm for a technology that appears to have innate advantages for safe resections has often given way to the strict limitations and demands of the neurosurgical operating theater. However, numerous creative solutions to improve laser delivery, power, safety, and ergonomics demonstrate the important role that technological advances in related scientific fields continue to offer neurosurgery. Benefiting from the most recent developments in materials science, current CO2 laser delivery systems provide a useful addition to the neurosurgical armamentarium when applied in the correct circumstances and reflect the important historical advances that come about from the interplay between neurosurgery and technology.
Stereotactic radiosurgery and the linear accelerator: accelerating electrons in neurosurgery
Authors: Rahman Maryam , Murad Gregory J. A. , Bova Frank , Friedman William A. , Mocco J
Published: September 2009

The search for efficacious, minimally invasive neurosurgical treatment has led to the development of the operating microscope, endovascular treatment, and endoscopic surgery. One of the most minimally invasive and exciting discoveries is the use of targeted, high-dose radiation for neurosurgical disorders. Radiosurgery is truly minimally invasive, delivering therapeutic energy to an accurately defined target without an incision, and has been used to treat a wide variety of pathological conditions, including benign and malignant brain tumors, vascular lesions such as arteriovenous malformations, and pain syndromes such as trigeminal neuralgia. Over the last 50 years, a tremendous amount of knowledge has been garnered, both about target volume and radiation delivery. This review covers the intense study of these concepts and the development of linear accelerators to deliver stereotactic radiosurgery. The fascinating history of stereotactic neurosurgery is reviewed, and a detailed account is given of the development of linear accelerators and their subsequent modification for radiosurgery.
Early history of the stereotactic apparatus in neurosurgery
Authors: Rahman Maryam , Murad Gregory J. A. , Mocco J
Published: September 2009

Stereotactic neurosurgery has a rich history, beginning with the first stereotactic frame described by Horsley and Clarke in 1908. It is now widely used for delivery of radiation, surgical targeting of electrodes, and resection to treat tumors, epilepsy, vascular malformations, and pain syndromes. These treatments are now available due to the pioneering efforts of neurosurgeons and scientists in the beginning of the 20th century. Their efforts focused on the development of stereotactic instruments for accurate lesion targeting. In this paper, the authors review the history of the stereotactic apparatus in the early 20th century, with a focus on the fascinating people key to its development.
Minimally invasive spine technology and minimally invasive spine surgery: a historical review
Authors: Oppenheimer Jeffrey H. , DeCastro Igor , McDonnell Dennis E.
Published: September 2009

The trend of using smaller operative corridors is seen in various surgical specialties. Neurosurgery has also recently embraced minimal access spine technique, and it has rapidly evolved over the past 2 decades. There has been a progression from needle access, small incisions with adaptation of the microscope, and automated percutaneous procedures to endoscopically and laparoscopically assisted procedures. More recently, new muscle-sparing technology has come into use with tubular access. This has now been adapted to the percutaneous placement of spinal instrumentation, including intervertebral spacers, rods, pedicle screws, facet screws, nucleus replacement devices, and artificial discs. New technologies involving hybrid procedures for the treatment of complex spine trauma are now on the horizon. Surgical corridors have been developed utilizing the interspinous space for X-STOP placement to treat lumbar stenosis in a minimally invasive fashion. The direct lateral retroperitoneal corridor has allowed for minimally invasive access to the anterior spine.

In this report the authors present a chronological, historical perspective of minimal access spine technique and minimally invasive technologies in the lumbar, thoracic, and cervical spine from 1967 through 2009. Due to a low rate of complications, minimal soft tissue trauma, and reduced blood loss, more spine procedures are being performed in this manner. Spine surgery now entails shorter hospital stays and often is carried out on an outpatient basis. With education, training, and further research, more of our traditional open surgical management will be augmented or replaced by these technologies and approaches in the future.
Anatomy, technology, art, and culture: toward a realistic perspective of the brain
Authors: Cavalcanti Daniel D. , Feindel William , Goodrich James T. , Dagi T. Forcht , Prestigiacomo Charles J. , Preul Mark C.
Published: September 2009

In the 15th century, brain illustration began to change from a schematic system that involved scant objective rendering of the brain, to accurate depictions based on anatomical dissections that demanded significant artistic talent. Notable examples of this innovation are the drawings of Leonardo da Vinci (1498–1504), Andreas Vesalius' association with the bottega of Titian to produce the drawings of Vesalius' De humani corporis fabrica (1543), and Christopher Wren's illustrations for Thomas Willis' Cerebri Anatome (1664). These works appeared during the Renaissance and Age of Enlightenment, when advances in brain imaging, or really brain rendering, reflected not only the abilities and dedications of the artists, but also the influences of important cultural and scientific factors. Anatomy and human dissection became popular social phenomena as well as scholarly pursuits, linked with the world of the fine arts. The working philosophy of these artists involved active participation in both anatomical study and illustration, and the belief that their discoveries of the natural world could best be communicated by rendering them in objective form (that is, with realistic perspective). From their studies emerged the beginning of contemporary brain imaging. In this article, the authors examine how the brain began to be imaged in realism within a cultural and scientific milieu that witnessed the emergence of anatomical dissection, the geometry of linear perspective, and the closer confluence of art and science.
Pre treatment by the crude and the n-hexane extract of Nigella sativa Linn. (Kalajira) alleviates diabetes mellitus
Authors: Matira K , Dewan ZF , Rehnuma TC , Farhana A , Zeba UN , Shahin S
Published: September 2009

Methodology: Effect of pretreatment by crude and n-Hexane extract of Nigella (10mg/kg body wt./day for 21 days) on streptozotocin (STZ, 50 mg/kg body wt. single dose i.p.) administered rats were observed in the present study. Biochemical parameters (Serum glucose, serum TG, serum cholesterol, pancreatic GSH) were compiled together with pancreatic histology. Results: Both the crude and the n-Hexane extract of Nigella pre-treated diabetic rats had demonstrated significant (P<0.001) alleviation from the elevated serum glucose, lowered pancreatic reduced glutathione (P<0.01) and elevated serum TG concentrations (P<0.01). 72% β cells appeared to be damaged by STZ administration, while in the crude and the n-Hexane extract of Nigella pretreated diabetic groups this damage was 31% and 46% respectively, the crude Nigella pretreated group thus appeared to have better amelioration. Conclusions: Further studies are suggested to obtain the protective ingredient from the crude Nigella and to observe its effect upon the above mentioned parameters of diabetic rats in higher doses for prolonged periods. Keywords: Diabetes, Nigella sativa Linn., Streptozotocin. doi: 10.3329/bjms.v8i1.3182 Bangladesh Journal of Medical Science Vol.8 No. 1-2; 2009 5-9
Evaluation of the antibody response against Hepatitis B Virus infection in patients on maintenance hemodialysis: A Pilot Study
Authors: Shahin S , Ali Md Khoybar , Farhana A , Matira K
Published: September 2009

Objective: This study was undertaken to evaluate the antibody response of hepatitis B virus infection in patients on maintenance hemodialysis (MHD) by detecting different viral markers. Method: Study subjects comprised a total of 88 chronic kidney disease (CKD) patients from Bangladesh Institute of Research and Rehabilitation in Diabetes, Endocrine and Metabolic Disorders (BIRDEM) and Bangabandhu Sheikh Mujib Medical University (BSMMU). Of them 63 patients on MHD and 25 predialysis patients served as cases and controls respectively. Clinical history was taken and serological markers for HBV (HBsAg, Anti-HBs, and Anti-HBc) were determined by using ELISA. Results: Hepatitis B virus was positive in 1.6% of maintenance hemodialysis (MHD) patients and in 16% of controls (p<0.02). Anti-HBc antibody was positive in 62% of dialysis patients and 72% of controls (p=NS) and the positivity was significantly associated in dialysis subjects with longer duration of dialysis (18 ± 22 vs. 10 ± 7, months, p<0.04), multiple units of blood transfusions (22 ± 29 vs. 10 ± 12, units, p<0.04) and more reuse of dialyzer (3 ± 1 vs. 2 ± 1, times, p<0.03) than the negative ones. Among MHD patients 84% were vaccinated against HBV with a schedule of 3 (79%) and 4 (21%) doses and protective antibody titer (>10 IU/L) was found in 57%. None of the controls were vaccinated but 66% had protective titer indicating post exposure natural immunity. Conclusions: Hepatitis B virus positivity was significantly higher among the predialysis subjects compared to dialysis group. Key words: Hepatitis B virus, Antibody response, Hemodialysis doi: 10.3329/bjms.v8i1.3185 Bangladesh Journal of Medical Science Vol.8 No. 1-2; 2009 15-21
Orthodontic treatment of mandibular anterior crowding
Authors: Alam MK
Published: September 2009

This paper concerns orthodontic treatment of a 17 years old Bangladeshi female with a class I malocclusion along with anterior crowding in the mandibular arch. Orthodontic treatment carried out with preadjusted Roth type (018 slot) fixed brackets with labial flaring of the mandibular incisors to accomplish the treatment. The esthetics and occlusion were maintained after retention. Key words: Crowding, malocclusion, labial flaring. doi: 10.3329/bjms.v8i1.3188 Bangladesh Journal of Medical Science Vol.8 No. 1-2; 2009 33-36
Intussusception in Children : A Study of 50 Cases
Authors: Jafor MA , Rahman M Latifur , Hoque S
Published: September 2009

This is a prospective study carried out at the department of surgery, Dhaka Shishu Hospital during the period from 1st February 1997 to 28th February, 1999. Fifty peadiatiric patients aged less than 12 yrs with provisional diagnosis of intussusception were included in this study. Highest number of patients were within 1 year of age (70%), male female ratio was 2.57:1, the exact aetiology of intussusception could not be indentified in majority of the cases (90%). Abdominal pain (82%), vomiting (78%) and per rectal bleeding (62%) was common presentations. All patients were managed surgically. Ileocolic type was commonest type of intussusception (66%). Postoperative complications was noted in 14% cases. With limited resources, this study tried to collect many information about various aspect of intussusception in Bangladeshi children. It is hoped that organization and compilation of these information will stimulate further studies, leading to a greater comprehension of the problems of intussusception of paediatric age groups in our country.   doi: 10.3329/taj.v18i2.3171 TAJ 2005; 18(2): 80-83
Femoral Head Diameters and Sex Differentiation in the Northern Zone (Rajshahi) of Bangladesh
Authors: Afroze Akhtari , Huda M Durrul
Published: September 2009

This study was aimed to find out the variations of the femoral head diameters in relation to sex in Bangladeshi people. The study was based on 123 paired human femurs (radiological view) of which 52 were male and 71were female. It was observed that the mean vertical and transverse diameters of the head of the male femur were significantly greater than that of female (P<0.001).No statistical significant difference was present between the measurement of the right and left side of the same sixth identification points that were derived from the vertical and transverse diameters of the head of the femur were higher in males than in females. The results showed that diameters of the femoral head as well as the identification points that are derived from them are of use in sex identification. The present study is of value to the forensic experts, orthopaedicians and prosthetists as it gives the idea about the dimensions of the femoral head in the present area.   doi: 10.3329/taj.v18i2.3172 TAJ 2005; 18(2): 84-88
Profile of Sexual Assault Cases Registered in the Department of Forensic Medicine, Rajshahi Medical College
Authors: Islam MM , Islam MR , Sarkar MA Mukit , Rashid MA
Published: September 2009

A cross sectional study was conducted among 291 victims of sexual assault cases examined at the department of Forensic Medicine, Rajshahi Medical College from February to June, 2004 in order to see the profiles of the sexual assault cases. In this study the mean age of the victims was 17.78 years. Out of 291 victims 3 individuals were male. The incidence of sexual assault was more frequent among the individuals aged from 14 to 18 years. The study should that 77.7% victims were unmarried. 80% individuals of sexual assault were inhabitants of rural areas and the rest of the victims were of urban areas. The study revealed that 88 (30.2%) had the signs of violence on their body. In finding out of the physical development the study presented that 86.9% victims had developed breast while 8.9% had not. Out of 288 female victims 84.72% female had old tear of hymen while 30 (10.41%) had recent hymenal tear. 1.4% victims of sexual assault showed presence of sperm in pathological examination.   doi: 10.3329/taj.v18i2.3174 TAJ 2005; 18(2):
Clinical Profile of Birth Asphyxia in Rajshahi Medical College Hospital
Authors: Haidary MH , Hussain Asgar , Ahmed Safiuddin , Kasem Abul
Published: September 2009

Birth asphyxia is an important cause of preventable cerebral injury in the neonatal period. It continues to be major cause of neonatal mortality and morbidity in both developing and developed countries. Recently a quite good number of birth asphyxiated new born babies had been admitted in the pediatric department of RMCH (Rajshahi Medical college Hospital). This study has been conducted to see the types and outcome of management of birth asphyxiated babies. A total 871 neonates were admitted in the pediatric department of RMCH from September 2001 to November 2002. Out of which birth asphyxia was 191 (21.92%) acute respiratory infection (ARI)-194 (22.73%), Low birth weight (LBW)-113 (12.97%), Neonatal jaundice-84 (9.64%), Septicaemia-38 (4.38%), Meningitis-26 (2.98%), Diarrhea-24 (2.75%), Birth trauma-24 (2.75%), Neonatal tetanus-04 (0.45%), Out of the total birth asphyxiated babies, mild type was 35 (18.32%), moderate type was 40 (20.94%), and severe birth asphyxia was 116 (60%), The recovery rate in mild birth asphyxia was (100%), in moderate case was (95%) and in severe case the rate was (74.13%).   doi: 10.3329/taj.v18i2.3176 TAJ 2005; 18(2):  106-108
In vitro Antimicrobial Activity of the Volatile Oil of Nigella Sativa Linn Seeds
Authors: Ara Nazma , Choudhury SAR , Amin Ruhul
Published: September 2009

The in-vitro antimicrobial activity of the Volatile oils of Nigella Sativa Linn Seeds was tested against fifteen pathogenic microbial strains includung three gram-positive, eleven gramnegative and a yeast Candida albicans. The volatile oil showed strong sensitivity to all the organisms. The zone of inhibition was found 13-32mm at a dose of 600μg/disc. Minimum inhibitory concentration (MIC) of the volatile oil was also determined against Staph. Aureus ATCC and E.coli ATCC were found 187μg/ml and 375μg/ml respectively.   doi: 10.3329/taj.v18i2.3177 TAJ 2005; 18(2): 109-112
Unusual Presentation of Hydatid Cyst
Authors: Mahbub NAM Golam
Published: September 2009

Affection of muscle by a hydatid cyst is rare. The clinical diagnosis of a hydatid cyst occurring in muscle is quite difficult. To reach to a diagnosis, a clinician should be cautious in taking proper history, doing necessary physical examinations & some investigations like ultrasonography, blood examination & fine needle aspiration. Removal of the cyst by surgery is the treatment of choice doi: 10.3329/taj.v18i2.3196 TAJ 2005; 18(2): 137-139
Breast Cancer: Overview of Modern Management
Authors: Uddin Dayem , Hannan ABM Abdul , Begum Khodeja Nahar
Published: September 2009

Potential benefits of local and or systemic therapy of breast cancer depending on the patient's stage. Local therapy would be expected to be most effective at a time when the patient's disease is confined within the ducts or lobules (premalignant or noninvasive) or is only minimally invasive. Local therapy would be expected to have little if any effect in patients with widespread systemic disease (macrometastatic), except in specific cases of isolated organ sites requiring palliation. Systemic therapy would be expected to have its greatest effect in prolonging survival in patients who are most likely to have distant metastases but whose disease has not had an opportunity to develop substantial resistance (micrometastatic), which might develop with ongoing tumor growth. However, tamoxifen may serve to suppers emergence of new primary cancer, and chest wall and surrounding lymph node radiation may prevent may prevent subsequent micrometastases.   doi: 10.3329/taj.v18i2.3197 TAJ 2005; 18(2): 140-143
Adherence Rates and Associations with Nonadherence in Patients with Rheumatoid Arthritis Using Disease Modifying Antirheumatic Drugs
Authors: van den BEMT BART J.F. , van den HOOGEN FRANK H.J. , BENRAAD BART , HEKSTER YECHIEL A. , van RIEL PIET L.C.M. , van LANKVELD WIM
Published: September 2009

Objective.

Nonadherence in patients with rheumatoid arthritis (RA) using disease modifying antirheumatic drugs (DMARD) may result in unnecessarily high levels of disease activity and function loss. The aim of this descriptive study was to assess adherence rates with self-report measures in a large random population, and to identify potential risk factors for nonadherence.

Methods.

A randomly selected sample of 228 patients with RA using DMARD was invited for a standardised interview. For each medicine, the patients were asked about adherence, consumption and perceived (side) effects. After the interview, the patients received self-report questionnaires to assess adherence [Compliance Questionnaire on Rheumatology (CQR) and the Medication Adherence Scale (MARS)], coping, beliefs about medicines, satisfaction about medicine information, and physical functioning. Subsequently, associations between adherence and demographics, clinical characteristics, and patient attitudes were examined.

Results.

Depending on the instrument used, 68% (CQR) and 60% (MARS) of the patients were adherent to DMARD. Nonadherence was not associated with demographic and clinical characteristics, satisfaction about information, medication concerns, and coping styles. The disease duration, the number of perceived side-effects, and beliefs about the necessity of the medicine were weakly associated with adherence.

Conclusion.

In this large study with a random RA population, 32%–40% of the patients did not adhere to their DMARD prescription. As none of the possible risk factors was strongly related to adherence, no general risk factor seems to be powerful enough as a possible screening tool or target for adherence-improving interventions. This implies that nonadherence barriers should be assessed on an individual basis.
What Factors Influence the Health Status of Patients with Rheumatoid Arthritis Measured by the SF-12v2 Health Survey and the Health Assessment Questionnaire?
Authors: LINDE LOUISE , SØRENSEN JAN , ØSTERGAARD MIKKEL , HØRSLEV-PETERSEN KIM , RASMUSSEN CLAUS , JENSEN DORTE VENDELBO , HETLAND MERETE LUND
Published: September 2009

Objective.

The Health Assessment Questionnaire Disability Index (HAQ) is a widely used outcome measure in rheumatoid arthritis (RA), whereas the SF-12v2 Health Survey (SF-12) was introduced recently. We investigated how the HAQ and SF-12 were associated with socio-demographic, lifestyle, and disease- and treatment-related factors in patients with RA.

Methods.

In RA patients from 11 Danish centers, clinical and patient-reported data, including the HAQ and SF-12, were collected. Three multiple linear regression models were estimated, with the HAQ, SF-12 physical component score (PCS), and SF-12 mental component score (MCS) as outcome and sociodemographic, lifestyle, and RA-related treatment and comorbidity characteristics as explanatory variables.

Results.

In total, 3156 (85%) of 3704 invited patients participated — 75% women, 76% rheumatoid factor-positive, median age 61 years (range 15–93 yrs), disease duration 7 years (range 0–68 yrs), Disease Activity Score on 28 joints (DAS28) 2.97 (range 0.96–8.61), HAQ score 0.63 (range 0–3), SF-12 PCS 56 (range 6–99), and SF-12 MCS 57 (range 16–99). Variation in HAQ was associated with 12 of 15 possible variables (R2 0.41), in PCS and MCS with 6 of 15 variables (R2 0.02 and 0.05). Patients with moderate to high DAS28 and ≥ 3 comorbid conditions had consistently worse HAQ and SF-12 scores compared to the reference groups, while weekly exercise was associated with better scores compared to no exercise.

Conclusion.

The HAQ was more sensitive to differences in demographic, lifestyle, and disease- and treatment-related factors than the SF-12. The established clinical value and feasibility of the HAQ highlights its advantages over the SF-12 in describing health status in RA.
Helicopter Laboratory Model Experiment With Web Access
Authors: Cvjetkovic Vladimir M , Matijevic Milan S , Grujovic Milan D , Stefanovic Miladin Z
Published: September 2009

This paper describes the experiment for learning and investigation of the helicopter laboratory model static and dynamic characteristics. Helicopter model is not the free flying one, as it has the two degrees of freedom â?? up / down movement and rotation with respect to vertical axis of the main propeller. The two basic different kinds of experiments with the helicopter model are possible. In the first group are experiments with the model for measurement of the static and dynamic characteristics that show the basic capabilities and overall performance of the model. Second group of experiments are control experiments for movement of the system to the desired position or for performing some continuous oscillatory movement. All experiments can be performed locally from the lab with the experimental setup and remotely. Remote experiments are performed by using the web user interface for controlling the laboratory equipment and the IP camera for observing the movements of the helicopter model.
Adapting a Remote Laboratory Architecture to Support Collaboration and Supervision
Authors: Lowe David , Berry Chris , Murray Steve , Lindsay Euan
Published: September 2009

Interest in, and use of, remote laboratories has been rapidly growing. These laboratories provide remote access, via the internet, to real laboratory equipment. Under appropriate circumstances they can support or even replace traditional (proximal) laboratories, provide improved access at reduced cost, and encourage inter-institutional sharing of expensive resources. Most attention to date has been on the development of the core infrastructure that manages access and interaction, and to a lesser extent consideration of pedagogic issues such as which learning outcomes are best suited to this modality. There has however been a recent recognition of the importance of also considering how collaboration and supervision can also be supported. In this paper we discuss a novel approach to the integration of support for multi-user distributed access to a single laboratory instance. The approach retains the benefits of the lightweight client inherent in the underlying architecture.
Fully-LabVIEW Powered Mössbauer Spectrometer
Authors: Pechousek Jiri , Prochazka Roman , Jancik Dalibor , Mashlan Miroslav
Published: September 2009

The virtual instrumentation techniques are applied for the first fully-LabVIEW powered Mössbauer spectrometer. The spectrometer application has to carry out several different tasks such as gamma-ray pulse height analysis (via digital oscilloscope), reference velocity signal generation for the motion of the radioactive source (via function generator) together with digital proportional-integral-derivative (PID) unit responsible to control the relative precise velocity between the source and the absorber (via CompactRIO) and Mössbauer spectra accumulation.
Lessons Taught and Learned from the Operation of the Solar Energy E-Learning Laboratory
Authors: Eleftheriou Polyvios C. , Michaelides Ioannis M.
Published: September 2009

The solar energy e learning laboratory (solar e-lab) in Cyprus is a good example of a web-based, remote engineering laboratory. It comprises a pilot solar energy conversion plant which is equipped with all necessary instrumentation, data acquisition, and communication devices needed for remote access, control, data collection and processing.

The impact that the solar e-lab had during its nearly 5 years of operation is indeed high. Throughout this period, the solar e-lab has been accessed by users from over 500 locations from 79 countries spread all over the world. In the period of November 2004 to October 2008, more than a million visits were recorded, out of which 25000 have registered on the site and surfed through studying the supplied material. Around 1000 hits concerned registered users that passed the pre-lab test and performed the experimentation part.

The four years of operation of the solar e-lab demonstrated how the Internet can be used as a tool to make the laboratory facilities accessible to engineering students and technicians located outside the laboratory, including overseas. In this way, the solar energy e-learning lab, its equipment and experimental facilities were made available and shared by a number of interested people, thus widening educational experiences. Judging from the online evaluation reports that were received from the solar e-lab users during the last 2 years of operation, it can be concluded that there is nearly excellent satisfaction by the users.
A Versatile Internet-Accessible Electronics Workbench with Troubleshooting Capabilities
Authors: Soumare Hamidou , Shroff Rahul , Hardison James L , Del Alamo Jesus A , Harward V Judson , Bailey Philip H , DeLong Kirky K
Published: September 2009

The MIT iLab Project was established to expand the range of laboratory experiences available to students in science and engineering education. iLabs are online laboratories that enable students to conduct real experiments remotely. Recently, the iLab Project has focused on building remote laboratories around the NI-ELVIS platform, an all-in-one electronics workbench. This paper will detail our recent efforts in expanding the capabilities of ELVIS-based iLabs by enabling students to test and debug digital and analog circuits. This work will enable students to perform remote experiments characterizing digital logic elements. By merging switching capabilities with the Digital Multimeter available on the ELVIS, students will have the ability to examine and troubleshoot circuits. These added capabilities will provide educators and students with unparalleled flexibility and significantly enrich the remote laboratory experience.
Fractal Analysis of EEG Signals in the Brain of Epileptic Rats, with and without Biocompatible Implanted Neuroreservoirs
Authors: López T. , Martínez-González C.L. , Manjarrez J. , Plascencia N. , Balankin Alexander S.
Published: September 2009

Current epilepsy rates in Mexico are 4% (SERSAME-Health Ministry), of which 80% correspond to Temporal Lobe Epilepsy (TLE). Antiepileptic drug administration is systemic, meaning that 90% of the active agent is lost between administration and delivery to the epileptic focus in the brain. Severe toxic secondary effects may occur as a result. The present study is aimed at developing an alternative antiepileptic drug delivery system. In this study, a sol-gel nanostructured titania device, in which valproic acid (VPA) has been encapsulated. This is a nanoparticulate device, which is biocompatible with brain tissue. Stereotactic surgery was used to implant the reservoirs in the temporal lobe of Wistar rats, using chemical kindling, which was used to induce epilepsy. The reservoir was designed to release the drug at a constant rate over a period of at least one year. A functional study was performed on the efficiency of drug delivery in order to evaluate the effect on spontaneous and induced neuron electrical activity. A new discovery, which is presented here, shows that in the case of damaged brain tissue, as is the case in epilepsy, the accumulation of red globules, oxygen transportation results in the formation of calcium carbonate crystals which surround the epileptic focus. Because these crystals have a specific polarization, we propose to characterize their influence on the EEG using statistical methods. The electrical activity was measured by electroencephalography using 5 healthy rats without and 5 rats with an implanted VPA/device. Cerebral signals describe the complex behavior of the brain dynamics as a function of time. Fractal algorithms are sensitive to fluctuations and lead to the analysis and characterization of this kind of complex phenomena. A systematic study of these EEG’s was made in order to observe the variation of signals during seizures and on the controlled rate of release of VPA. We have estimated the Hurst exponent (H) to measure long range-dependence. Preliminary results show that for the control group, signal behavior is persistent (H>0.5), while for the epileptic group antipersistency was observed (H<0.5), with variations due seizure stages. During the protection period using VPA, preliminary results show that values tend to reach original behavior, as the crisis is stabilized.
Parametric Analysis of Perfect Matched Layer Model of Finite Difference Time Domain Method
Authors: Benavides-Cruz M. , Nieto-Rodríguez M. , Enciso-Aguilar Mauro , Galaz-Larios Martha , Sosa-Pedroza J.
Published: September 2009

The parametric analysis of the electrical conductivity distribution for the Perfect Matched Layer (PML) method, is discussed in this communication. The Berenger’s PML defines a new computational space around the area of interest yielding to reduce any undesirable reflection that may perturb the main computational domain. The optimal parameters values for the conductivity distribution are obtained in order to provide lower levels of reflection, given raise to model infinite electromagnetic propagation spaces and as a consequence, to optimize the computing resources.
Laminar Flow through a Rectangular Horizontal Channel with Asymmetrical Contraction
Authors: Morales-Contreras O.A. , Barbosa-Saldaña J.G. , Jiménez-Bernal J.A. , Gutiérrez Torres Claudia del Carmen
Published: September 2009

Numerical simulation for the three-dimensional laminar flow through a forward facing step channel was simulated by Fluent 6.3 code. Four Reynolds numbers and four step lengths were analyzed. The results showed that the length of the recirculation zone upstream the step depends on Reynolds number, as well as on the step height (h), while the height of the recirculation zone extends about 70% of the step height. In addition, it was found that the velocity profile in the stream direction at the channel exit presents a fully developed profile for the axial component. Nonetheless, the profile along the transversal direction does not have a parabolic profile, even for a length of 60h
Influence of the Alignment of Two Airfoils in the Losses Generation
Authors: Moreno-Pacheco Luis A. , Valle-Meléndez G.E. , Gutiérrez Torres Claudia del Carmen , Jiménez-Bernal J.A. , Toledo-Velázquez M.
Published: September 2009

A numerical simulation of a flow passing throw two NACA 0012 airfoils is presented in this paper. Aerodynamics, drag forces, and pressure drop is quantified when both profiles are axially aligned and then when one of them is vertically displaced. NUMECA code and Spalart-Allmaras turbulence model were used for this purpose. The results showed that aerodynamic losses are present in both profiles, meaning that the presence of the back profile plays an important role in the aerodynamic behavior of the frontal profile.
Theoretical and Experimental Analysis of Turbulent Liquid Film Flowing down a Vertical Surface
Authors: Sinkunas Stasys , Gylys Jonas , Kiela Algimantas
Published: September 2009

The purpose of the present study is to obtain a comprehension for the momentum and heat transfer developments in gravitational liquid film flow. Analytical study of stabilized heat transfer for turbulent film was performed. A calculation method of the local heat transfer coefficient for a turbulent film falling down a vertical convex surface was proposed. The dependence of heat flux variation upon the distance from the wetted surface has been established analytically. Experimental study of velocity profiles for turbulent liquid film flow in the entrance region is performed as well. Analysis of profiles allowed estimating the length of stabilization for turbulent film flow under different initial velocities.
Synthesis Optimization of Planar Mechanisms
Authors: Lugo-González E. , Merchán-Cruz E.A. , Hernández-Gómez Luis Héctor
Published: September 2009

This work presents an approach based on Genetic Algorithms (GA) for the dimensional synthesis of planar mechanisms as path generators. The study case deals with the development of a four-bar mechanism with application to lower limb prosthesis, specifically the knee joint. The optimization algorithm contains the objective function defined by the synthesis problem and the representation of a set of mathematical relationships that describe the kinematic restrictions of the planar mechanism. The objective function is a given numerical value for every solution that corresponds to the best possible mechanism. In other words, this objective function is the determinant to minimize the error between the desired and the generated points and can be affected by the lengths of the links, the transmission angles, the Grashof conditions, type of mechanisms, etc. The population, crossover or mutation in the GA determines the exactitude in the results. The first goal of this work is to find the optimal dimensions of the links to minimize the error between the actual coupler curve and the desired path.
Resolution of a 3 RRR Planar Parallel Mechanism
Authors: Yáñez-Valdez R. , Ruiz-Torres M. , Morales-Sánchez E. , Castillo-Castañeda E. , Briones-León J.A.
Published: September 2009

This paper proposes a methodology to analyze the resolution and variations in the positions of the 3RRR planar parallel mechanism driven by electrical actuators of discrete steps. This methodology consists of graphing and plotting all the possible combinations of angular movements of a three legs mechanism. This generates a “cloud of points” that will be the boundary of the control limits, so as to find the closest trajectory to a straight line. It was found that resolution, accuracy, and the approximation error improves when micro-steps are employed. For this purpose, it is necessary to determine direct and inverse kinematics, in order to calculate the workspace. A prototype was built to validate the methodology proposed.
Synthesis of 4C Mechanism for Generation of a Dual Mathematic Function
Authors: García-Ríos I. , Palacios-Montufar C. , Flores Campos J.A. , Osorio-Saucedo R.
Published: September 2009

In this paper, the synthesis of a spatial mechanism with a 4C topology (four cylindrical joints) to generate a dual mathematic function is presented. The mechanism has two real degrees of freedom (2 DOF) and each of them generates an output function. The dual algebra is used as a convenient tool for solving problems with topological features of this type of mechanisms. The design equations are separated into two parts: the first one is the primary part and the second one corresponds to the dual number. The numerical solution of the equations are given and verified by computer simulation.
Stress and Vibration Analysis of a Lathe Bed Made of Aluminum-Copper Alloy for High Speed Machining
Authors: Torres-Martínez R. , Urriolagoitia-Calderón G. , Urriolagoitia-Sosa G. , Espinoza-Bustos R.
Published: September 2009

The analysis of the rigidity of an Al-Cu alloy lathe bed to be used for high speed machining (HSM) is presented in this work. Mechanical design optimization by means of simulations based on the finite element method (FEM) was applied in order to calculate the lathe bed deflections, the natural frequencies and the corresponding vibration amplitudes. For the parametric modeling, a prototype lathe to be used in conventional speed machining (CSM) with a cast iron bed was considered. The optimized parameter was the stress in the lathe bed, considering as a restriction the allowable deflection in a node of the machine-tool structure. The design variables were the height, the thickness, and the length of the wall of the lathe bed. The lathe bed was loaded with cutting and inertial forces due to HSM in order to demonstrate that the evaluated stresses and vibration amplitudes are in an acceptable level according to ISO Standards (system of limits and fits in workpieces). The results show the feasibility of using an Al-Cu alloy instead of cast iron in the fabrication of lathe beds. This increases the flexibility of manufacture.
Algorithm for Estimating Natural Frequencies and Mode Shapes of Cantilever MEMS Microbeams
Authors: Flores-Herrera L.A. , Merchán-Cruz E.A. , Velázquez-Sánchez A.T. , Rivera-Blas R.
Published: September 2009

The use in the past of mathematical techniques and methodologies to design macro-world structures in the past are now considered for designing micro-world structures. In this work, a computational algorithm for estimating natural frequencies and mode shapes of cantilever microbeams is presented. The methodology is based on the Rayleigh-Ritz method, which considers the potential and kinetic energies of the mechanical system. A proposed polynomial equation is first considered to establish the behavior of the microstructure. Together with the energy equations, an eigenvalue problem is constructed. The corresponding eigenvalues give an approximate estimation of the frequency values; the corresponding eigenvectors once substituted in the proposed polynomial describe the mode shapes of the microbeam for each frequency value. The results obtained with this methodology were compared with the finite element method. An interesting difference between the methodologies and the algorithm was found and the corresponding results are shown.
Mechanics of Randomly Folded Thin Materials
Authors: Susarrey Huerta Orlando , Mendoza Nuñez Maribel , Tamayo Meza Pedro A. , Balankin Alexander S.
Published: September 2009

In this work, the mechanical properties of randomly folded thin sheets in the hydrostatic and non-hydrostatic stress states were studied. It is pointed out that under the hydrostatic compression the sheet, rigidity is governed by the volume dependence of its enthalpy, whereas in a non-hydrostatic stress state, the rigidity of folded sheets is controlled by the shape dependence of the Edwards entropy of the network of crumpling creases. Furthermore, the stress relaxation in folded sheets after uni-axial compression was studied. It was found that stress relaxation in folded elasto-plastic sheets differs from this in the folded predominantly plastic sheets and obeys an unusual relaxation law with the universal characteristic exponent.
Rotating Bending Fatigue Tests on Aluminum Alloy AISI-SAE 6061-T6 at High Speed (150 Hz), and Close to Elastic Limit
Authors: Domínguez Almaraz Gonzalo , Tapia Silva Edgar , Guzmán Tapia Mauricio , Villalón López Jesús
Published: September 2009

This work deals with rotating bending fatigue tests at high speed (150 Hz), carried out on aluminum alloy AISI-SAE 6061-T6 for which the highest experimental stress inside the specimen is close to the elastic limit of material. Simulation results are obtained by Visual Nastran software in order to determine the numerical stress and strain distributions inside the specimen; then, this information is used for the experimental set up. A general description of experimental test machine and experimental conditions are developed in first sections, following section present the experimental results and discussion about the observed failure origin related to discontinuities and the associated high stress zones. A principal contribution of this work is related to the analysis of fracture surfaces and its correlation with experimental fatigue endurance: a simple model is proposed for the prediction of fatigue life of this aluminum alloy under high speed rotating bending fatigue tests, based on the surface density of associated fatigue macro-plastic deformation zones close the crack initiation.
Fatigue Crack Growth in SAW Welded Joints of API 5L Steel Pipe in the Short Radial Direction
Authors: Angeles Herrera D. , González Velázquez J.L.
Published: September 2009

The fatigue crack growth of longitudinal SAW welds of a API 5L X42 steel pipe was evaluated using curved three point bend test specimens, where the radius of curvature of the specimens was equal to the pipe radius, so that no extensive machining or flattening was required. The fatigue crack growth tests were done in a servohydraulic closed loop machine under load control, in air at room temperature. The da/dN vs ∆K plots and Paris’s equation constants were obtained for the base metal, deposited metal and heat affected zone in the CR orientation, which corresponds to the short transverse direction of the pipe. The greater resistance to fatigue crack growth was the base metal, whereas the deposited metal showed the least resistance to the fatigue crack propagation. The deposited metal and the heat affected zone behaved according to Paris’s law, unlike the base metal, that showed a high dispersion of the fatigue crack growth rates. This behavior was due to the propagation of the crack in the direction transverse to the banded microstructure. Furthermore, the differences in fatigue crack growth rates among each zone were also related to the roughness of the fracture surfaces and fracture toughness.
Investigation of Curing Process on Melt Spun Polymethylsilsesquioxane Fiber as Precursor for Silicon Oxycarbide Fibers
Authors: Narisawa Masaki , Sumimoto Ryuichi , Kita Kenichiro , Mabuchi Hiroshi , Kim Young Wook , Sugimoto Masaki , Yoshikawa Masahito
Published: September 2009

Polymethylsilsesquioxane (PMSQ) fiber was exposed to metal chloride vapors in a controlled atmosphere or electron beam irradiation in air to promote the curing process. The cured fibers were pyrolyzed at 1273K to compare the efficiency of individual curing method. The cured fibers were investigated by FT-IR, an optical microscope and TG analysis. In the case of successful curing, averaged diameter and tensile strength were analyzed on the obtained Si-O-C fibers.
Low-Temperature Sintering and Microwave Dielectric Properties of the Zn2SiO4 Ceramics
Authors: Dai Ying , Sun Yao , Chen Wen
Published: September 2009

Willemite ceramics (Zn2SiO4) possess excellent millimeter-wave dielectric properties, but it also has a high sintering temperature above 1300°C by traditional solid-state reaction and relatively large negative τf value. Zn2SiO4 nanoparticles synthesized by Sol–Gel method were used to improve the sintering and dielectric properties of the Zn2SiO4 ceramics. Using the nanoparticles, Zn2SiO4 ceramics can be sintered at a low temperature, 1150°C and exhibited improved microwave dielectric properties of εr =6.62, Q × f=24500 GHz, τf =-59ppm/°C. By adding TiO2 with high positive τf value (+450 ppm/°C) and CuO as sintering aid, near zero τf value and low sintering temperature can be achieved. With 11wt% of TiO2 and 5 wt% of CuO, an εr value of 9.3, a Q × f value of 12200GHz and a τf value of -11 ppm/°C were obtained at 1000°C, confirming the promising potential of the CuO-added TiO2-Zn2SiO4 ceramics as candidate materials for low–temperature cofired ceramic (LTCC) devices.
Preparation of Fine Mullite Powder in a SHS Chemical Furnace System
Authors: Yang Yu , Wang Yu Cheng , Fu Zheng Yi , Wang Wei Min , Wang Hao , Zhang Jin Yong
Published: September 2009

Within a very short heating period, fine mullite powder with practicle size below 1µm was obtained in a novel synthesis system, a self-propagating high-temperature synthesis (SHS) chemical furnace, from which the tremendous heating derived. The combustion reactants consisting of Ni, Al and TiC were chosen as a chemical furnace in this system to supply the heat, calcining temperature was increased at a heating rate of 1350K/min in the heating process, till the maximum temperature (1350°C). The rapid mullitization process was performed within 1 min, microstructure analysis indicated that small mullite grains (<50nm) were crystallized, fine mullite particles (<1µm) with narrow particle size distribution, favorable activity for sintering were derived. And significant grain growth was observed in mullite powder, when the combustion reactants consisting of Ni, Al and <30 mol.% TiC.