AXSIS (Yeditepe Üniversitesi)
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High resolution discreate optical absorption spectra of spectroscopically pure silicon dioxide in UV-C
No full textUltraviolet light induced high resolution optical absorption spectra of high purity silicon dioxide have been studied. An ultraviolet discreate absorption spectra were recorded photographically between 200-300 nm. Resonance fluorescence was observed at 288.2 nm, and around this region, Raman resonance scattering were also recorded at room temperature by flash photolysis technique.The Yeditepe University Open Access System is a compendium of indexed publications. Copyright and usage rights may be held by publishers and/or authors. The collection was established for the scientific publications prepared by Yeditepe University academicians and is to be found in the institutional archive
Lengthening of replanted or revascularized lower limbs: Is length discrepancy a contraindication for limb salvage?
No full textSome replantation cases require substantial bone shortening for primary closure. Leg-length discrepancy can be restored by lengthening of the replanted or revascularized extremities. Between 1991 and 2000, four patients with four total and two subtotal below-knee amputations had replantation or revascularization for their severely damaged extremities. All of them had extensive debridement, vascular repair, bone shortening and nerve repair for sensibility of their soles. One of the replanted extremities failed and had to undergo below-knee amputation because of sepsis. No other infection or vascular complications were encountered following the replantations or revascularizations. After bony consolidation, four legs were lengthened; for elimination of length discrepancy in three cases, and for obtaining balanced body proportion in one case in which the other leg was also amputated. In all procedures, a unilateral dynamic axial external fixator was used. The lengthening was performed from the proximal tibial metaphysis, with a subperiosteal osteotomy. Evaluation of injury according to the Mangled Extremity Severity Score (MESS) would encourage the surgeon to avoid salvage surgery with a shortened extremity, because of the required debridement of soft tissue and bone. These authors think the amount of limb shortening is not a major criterion in evaluating a traumatic total or subtotal below-knee amputation for salvage replantation or revascularization. A knee that has stable joint motion and the possibility of preservation of sensibility of the sole broadens the scope of indications for limb salvage, even with deliberate shortening that can be restored by lengthening; length discrepancy is not a contraindication for limb salvage.The Yeditepe University Open Access System is a compendium of indexed publications. Copyright and usage rights may be held by publishers and/or authors. The collection was established for the scientific publications prepared by Yeditepe University academicians and is to be found in the institutional archive
The distribution of foreign direct investments in the service sector in Istanbul
No full textTurkey adopted neo-liberal policies in order to increase its economic integration into international relations after 1980. As a result of these measures, foreign direct investment (FDI) inflows increased greatly and Istanbul became the prime site for foreign firms operating in Turkey's various service sectors, such as financial, producer and distributive services. The location preferences of the foreign firms were generally in parallel with the development of the central business district (CBD) of Istanbul, although in some cases the location preferences of the foreign investors contributed to the emergence of new center extensions. © 2002 Elsevier Science Ltd. All rights reserved.The Yeditepe University Open Access System is a compendium of indexed publications. Copyright and usage rights may be held by publishers and/or authors. The collection was established for the scientific publications prepared by Yeditepe University academicians and is to be found in the institutional archive
Integrating expert knowledge in environmental site characterization
No full textThe site characterization issue is the most essential task to be undertaken prior to the reclamation of a potentially contaminated site and it is composed of sampling, laboratory analysis, and data evaluation phases. We are primarily concerned with the data evaluation phase and we utilize a recently developed adaptive areal partitioning algorithm to characterize the site. Here, we enhance this approach by integrating expert knowledge (expert belief) into the fuzzy areal assessment scheme which derives information from sample data. We propose to allocate an adaptive weight to expert belief during the assessment. We compare the belief-integrated approach with the nonintegrated one on synthetically generated sites where both uniform and biased sampling have been applied independently. In biased sampling, the zones claimed to be highly contaminated (by the expert) are allocated a higher sampling density. We demonstrate that the belief-integrated approach outperforms the nonintegrated one both when the expert is correct or mistaken in his/her judgment irrespective of the sampling methodology.The Yeditepe University Open Access System is a compendium of indexed publications. Copyright and usage rights may be held by publishers and/or authors. The collection was established for the scientific publications prepared by Yeditepe University academicians and is to be found in the institutional archive
Comparison of serum and bronchoalveolar lavage fluid sialic acid levels between malignant and benign lung diseases
No full textBackground: It is known that tissue and serum sialic acid levels may be altered by malignant transformation. In this study, sialic acid levels were determined in bronchoalveolar lavage fluid (BAL) and serum in two groups of patients with lung cancer and non-malignant diseases of the lung.The Yeditepe University Open Access System is a compendium of indexed publications. Copyright and usage rights may be held by publishers and/or authors. The collection was established for the scientific publications prepared by Yeditepe University academicians and is to be found in the institutional archive.Colorimetric methods were used for determination sialic acid in serum and in BAL samples. Flexible bronchoscopy was used to obtain the latter
Uncertainty Modelling in Software Development Projects (With Case Study)
No full textA project scheduling model tailored specifically for software development projects is proposed in this study. The model incorporates uncertainties related to activity durations and network topology. The first type of uncertainty exists due to error-prone coding which might result in elongated task durations caused by validation and debugging sessions. Furthermore, in practice, macro-activities represent groups of sub-tasks in order to simplify the planning and monitoring of the project. Due to the aggregation, it is more difficult to be precise on the duration of a macro-activity. The uncertainty related to the network topology is due to common database design issues or program modules shared among parallel tasks in the project network. These tasks become associated with each other through uncertain Start-to-Start (SS) precedence relationships. On the other hand, SS lags may also be the outcome of technological precedence relationships among pairs of activities. However, the imprecision underlying the work content of a predecessor activity leads to uncertain SS lags. Software development projects are human-intensive projects and hence, the duration of a task depends on the skill of the person assigned to the job as well as his/her learning rate. Thus, a task may be realized by alternative staff members which results in different expected task durations. Hence, a realistic model proposed for software development projects should incorporate staff assignment features under the uncertainties discussed above. In this study, we develop a mathematical model for software development projects and propose heuristic solution methods to be used by the project co-ordinator in preparing the project plan. The heuristic algorithms developed here are tested on real data provided by a consulting firm undertaking software development projects from manufacturing companies in Turkey.The Yeditepe University Open Access System is a compendium of indexed publications. Copyright and usage rights may be held by publishers and/or authors. The collection was established for the scientific publications prepared by Yeditepe University academicians and is to be found in the institutional archive
Nickel and Chromium Levels in the Saliva and Serum of Patients with Fixed Orthodontic Appliances
No full textThe aim of this study was to evaluate the concentrations of nickel and chromium ions in salivary and serum samples from patients treated with fixed orthodontic appliances. A second aim of this study was to determine any significant changes in these concentrations during any period of the treatment time. Saliva and blood samples were collected from 100 patients ranging in age from 12 to 33 years. Twenty samples from each group were obtained. The groups were as follows: In the first group, saliva and blood samples were collected before insertion of the fixed appliances. In the second, third, fourth, and fifth groups, samples were collected at 1 week, 1 month, 1 year, and 2 years after appliance insertion. The serum was prepared by centrifuging the blood samples at 3000 rpm for 10 minutes. The fixed appliances consisted of an average of 4 bands and 20 bonded brackets. No palatal or lingual appliances welded to bands or extraoral auxiliary appliances were used. The spectrophotometric determinations were carried out using electrothermal atomic absorption spectrophotometry. The results indicated certain differences in the amounts of nickel and chromium released from fixed orthodontic appliances during different periods of treatment. The Mann-Whitney U-test from the SPSS statistics program was used to analyze the significance of the differences between no-appliance samples and those obtained with the appliances present. In the serum, there were statistically significant increases in ion concentration in the second-year groups. In saliva samples, nickel and chromium reached their highest levels in the first month and decreased to their initial level in the rest of the groups. It can be concluded that fixed orthodontic appliances release measurable amount of nickel and chromium when placed in the mouth, but this increase doesn't reach toxic levels for nickel and chromium in the saliva and serum.The Yeditepe University Open Access System is a compendium of indexed publications. Copyright and usage rights may be held by publishers and/or authors. The collection was established for the scientific publications prepared by Yeditepe University academicians and is to be found in the institutional archive.The patients in this study were treated in the Department of Orthodontics, Faculty of Dentistry, University of Marmara. Saliva and blood samples were collected from 100 patients (67 females and 33 males) ranging from 12 to 33 years of age, with an average age of 19.5 years. Salivary and blood samples were taken from patients who were treated using fixed orthodontic appliances. Orthodontic appliances consisted of an average of 4 bands and 20 bonded brackets manufactured by Unitek (Monrovia, California), nickel titanium wires manufactured by Ormco (Glendora, California), and stainless steel wires manufactured by Unitek.Criteria of patient inclusion were as follows:Patients were in the permanent dentition period,Patients did not have any amalgam fillings and metal restorations, which could any galvanic corrosion in the mouth,Patients had standard edgewise brackets on the incisors, canines, and premolars and standard edgewise bands on the first molars,Patients did not have any palatal or lingual appliances welded to the bands (ie, rapid maxillary expansion appliance) or extraoral auxiliary orthodontic appliances (ie, headgear).In order to determine salivary and serum nickel and chromium levels during different periods of treatment, 20 samples from each group were obtained. The groups were as follows: In the first group, saliva and blood samples were collected before insertion of the fixed appliances. In the second, third, fourth, and fifth groups, samples were collected 1 week, 1 month, 1 year, and 2 years after appliance insertion, respectively.All saliva samples were collected in the morning before breakfast. The patients rinsed their mouths thoroughly with deionized and distilled water before the collection. Saliva was sampled for 5 minutes with the mouth closed without stimulation and transferred to plastic test tubes. Blood was obtained from the antecubital fossa of the arm and centrifuged at 3000 rpm for 10 minutes in order to prepare the serum. Acid-washed plastic containers were used for storage of saliva and serum samples. The samples were kept at −20°C until they were processed.The spectrophotometric determinations were carried out using an electrothermal atomic absorption spectrophotometer in Uludağ University Faculty of Medicine (Unicam 90 Graphite Furnace, ATI Unicam 929 AAS). Before the analysis, samples were centrifuged at 3000 rpm for 10 minutes to settle particulate matter. A calibration curve was made from the results obtained with standard solutions prepared with the same reagents as those used for the serum samples. Synthetic saliva was used for the calibration curve made for the salivary analysis. Each test was analyzed 3 times and the average was used as the result. Before each test, 1 distilled water sample was processed in order to prevent possible contamination. The insoluble precipitate was not included in the analysis because of the problem of particles causing variation in the results.The Mann-Whitney U-test from the SPSS statistics program was used for statistical analysis of the results. The statistically significant differences were analyzed in 5 different periods of treatment time for the 4 main groups, which included chromium in saliva, nickel in saliva, chromium in serum, and nickel in serum
Photophysical properties of 5H-dibenzo[a,d]cycloheptene in solution
No full textA number of photophysical properties of 5H-dibenzo[a,d]cycloheptene have been measured including the decay parameters of the lowest excited singlet and triplet states. Molecules were excited in a two-step process. In the first step, S1 is created which undergoes intersystem crossing to T1, then T-T absorption creates an excited triplet molecule which returns to the first excited singlet level by intersystem crossing. The recreated first excited singlet state decays back to the ground state by emitting B-type of delayed fluorescence.The Yeditepe University Open Access System is a compendium of indexed publications. Copyright and usage rights may be held by publishers and/or authors. The collection was established for the scientific publications prepared by Yeditepe University academicians and is to be found in the institutional archive
Electronic spectra and excited state properties of triptycene in solution
No full textAbsorption, emission and some excited state lifetimes are measured at room temperature and at 77 K in solution. B-Type delayed fluorescence decay time is reported for the first time for triptycene. The results are compared with the findings of photolysis, flash photolysis and laser flash photolysis experiments.The Yeditepe University Open Access System is a compendium of indexed publications. Copyright and usage rights may be held by publishers and/or authors. The collection was established for the scientific publications prepared by Yeditepe University academicians and is to be found in the institutional archive
Cross-correlation noise studies in atomic magnet-optic rotation spectroscopy
No full textAnalytical signals in an Atomic Magneto-Optic Rotation spectrometer are buried noise at the limit of detection. The noisy analytical signals were analysed by carrying out mathematical correlation of their time domain waveforms. The noise components of signals were removed by auto-correlation to simplify the study. If noise interferes in analytical signals whose source is unclear, a cross-correlation of the output waveform with noise source may identify the source, e.g., mains frequencies and background radio signals. A cross-correlation will reveal whether the two signals are derived from the same source. This can also lead to an improvement in the signal detection limit. Either of the two above situations can occur in studying analytical signals. In this study, both auto-and cross-correlation studies were carried out on analytical signals which had discrete noise sources present in their waveforms.The Yeditepe University Open Access System is a compendium of indexed publications. Copyright and usage rights may be held by publishers and/or authors. The collection was established for the scientific publications prepared by Yeditepe University academicians and is to be found in the institutional archive