An experimental and computational study on efficiency of white LED packages with a thermocaloric approach

Thermal management of light-emitting diode (LED) chips is crucial for light extraction and lifetime. It is well known that the light output of an LED decreases with the elevated temperatures. For higher light extraction, the power input to the chip should be substantially high leading nonuniform current spreading and local joule heating at the chip active layers. However, this leads to a high amount of heat generation at the chip and a considerable amount of increase in the junction temperature. Besides shortening the lifetime of the chip, it also strongly affects the light output of the system. Although nominal driving currents for LEDs are around 350-400 mA, the ideal operating condition for the cost effectiveness at higher driving currents and corresponding efficiency of an LED chip is to be explored. In this paper, LED chips' thermal and optical behaviors were investigated for different driving conditions while the board temperature is controlled using a thermoelectric cooler and the input current to the chip. The system was numerically investigated using a computational fluid dynamics software and validated with experimental studies. Consequently, a correlation for efficiency covering a wide range of operating conditions is presented. The efficiency of the LED that is obtained for 30 °C is 42%, whereas it drops to 30% for 50 °C board temperature. If one assumes a logarithmic relationship between the efficiency and the board temperature, the efficiency is expected to be around 20% for a typical LED operating temperature of between 80 °C and 100 °C.European Union ; the Istanbul Development Agency

Immunohistochemical Analysis Of Cd31, Cd36, And Cd44 Antigens In Human Omentum

Objective: Milky spots in the human omental tissue are known to be consisting of lymphocytes, macrophages and mast cells. Our goal was to evaluate the relationship of lymphoid cells and macrophages with vasculature and stromal components. Methods: In this study we examined the biopsy specimens obtained from the adult patients whom were operated for different purposes in the General Surgery Department of Dicle University Hospital, Ankara, Turkey. We used CD31 as an endothelial cell marker, CD36 which is known to react with microvascular endothelium and adipocytes, and CD44 which is a hyaluronic acid receptor using an indirect immunoperoxidase technique. Results: We observed that CD31 was mainly reactive with vascular endothelial cells and platelets, CD36 was reactive with microvascular endothelium and adipocytes and CD44 was mainly expressed by the endothelial cells of high endothelial venules, fibroblasts in stromal compartments and by large mononuclear cells. Conclusion: We determined the structural and immunophenotypic features of omental lymphoid tissue components stressing vascular and stromal elements, and we briefly discussed the significance of the expression of these molecules in the determined locations.Wo

Structural And Immunophenotypic Characterization Of High Endothelial Venules In Rat And Human Tissue

Objective: To present additional data on high endothelial venule (HEV) structure and immunophenotype. Methods: We used the zinc iodide-osmium tetroxide technique (ZIO), which is a metallophilic fixation and staining technique to examine HEVs at light and electron microscopic levels as this technique was previously reported to be reactive with cells in HEVs. Tonsils and lymph nodes were obtained from the Surgery and Otorhinolaryngology Departments, Hacettepe University Hospital, Ankara, Turkey during 2002 and 2003. An indirect immunohistochemical technique was used to examine frozen human tissue samples. Results: Organelle rich high endothelial cells, sheet-like processes of pericytes surrounding HEVs, structural relation of pericyte processes with fibroblastic reticular cells, an unusual multivesicular body-like organelle within high endothelial cells were presented. Expression of a large panel of defined and yet non-defined antigens on HEVs are also presented using an indirect immunoperoxidase technique. Conclusion: Presence of some of these antigens on HEVs was previously reported while no previous report is available for others. Significance of the expression of these antigens in HEVs, structural hints for trans endothelial migration of lymphocytes and their travel along the reticular cell meshwork is briefly discussed.Wo

A comparative study of oculomotor, trochlear and abducens nerves in Arabian foals

BAHAR, SADULLAH/0000-0002-6423-6499; ILGIN, CAN/0000-0003-1751-8546WOS: 000398130800010PubMed: 28296553We investigated the microscopic structure of transverse sections of the oculomotor, trochlear and abducens nerves of Arabian foals using stereological methods. Bilateral nerve pairs from 2month-old female Arabian foals were analyzed. The tissues were embedded in plastic blocks, then 1 mu m thick sections were cut and stained with osmium tetroxide and methylene blue-azure II. Stereology was performed using light microscopy. Morphometry showed that the right and left pairs of nerves were similar. The transverse sectional areas of the oculomotor, trochlear and abducens nerves were 1.93 +/- 0.19 mm(2), 0.32 +/- 0.06 mm(2) and 0.70 +/- 0.08 mm(2), respectively. The oculomotor nerve exhibited a significantly greater number of myelinated axons (16755 +/- 1279) and trochlear (2656 +/- 494) and the abducens nerves (4468 +/- 447). The ratio of the axon diameter to myelinated nerve fiber diameter was 0.58, 0.55 and 0.55 for the oculomotor, trochlear and abducens nerves, respectively. Of the three nerves studied, the abducens nerve exhibited the greatest nerve fiber area, myelin area, nerve and axon diameters, and myelin thickness. The ratio of small myelinated nerve fibers was greatest in the oculomotor nerve.Kirikkale University Scientific Research CouncilKirikkale University [2012/57]Our study was supported by a grant from the Kirikkale University Scientific Research Council (Project no: 2012/57)

Volumetric Assessment of Lateral Pterygoid Muscle in Unilateral Chewing: A Stereologic Study

WOS: 000270369000013PubMed ID: 19816257Unilateral chewing habit is common in dentate populations. It may initiate a hypertrophy process in the lateral pterygoid muscles compared with the nonused sides. We hypothesized that the lateral pterygoid muscles of the affected sides would be larger in volume than those of the nonaffected sides in subjects with unilateral chewing habit. Because analysis of medical images in accordance with the rules of modem stereology enables precise unbiased estimates of muscle volume, and magnetic resonance imaging (MRI) is a criterion standard as an imaging modality for the analysis of muscles because of its excellent soft-tissue resolution, we estimated lateral pterygoid muscle volume both at fight and left sides using stereologic techniques (Cavalieri principle) by means of MRI. The MRI-estimated volumes of both the inferior and the superior heads of the lateral pterygoid muscle at the chewing side were significantly greater than the opposite side when compared. This finding may assist in the interpretation of lateral pterygoid muscle and temporomandibular joint-related problems in maxillofacial surgery clinics. This investigation has also demonstrated that systematically sampled MRI slices through the lateral pterygoid muscle can be used to obtain unbiased estimates

Küçük hücreli dışı akciǧer kanserli hastalarda CD14 ve CD44S ekspresyonu

Objective: Lung cancer is one of the most common cancers with high mortality. Only 10-15% of the patients with lung cancer survive more than five years despite advanced treatment strategies. Features of tumor immunity are important in carcinogenesis, and immunological mechanisms must be clarified. The role of CD14 and CD44s proteins in tumor immunity of lung cancer is controversial, and studies on these proteins mostly were held on cancer cell lines. In this study, we aimed to investigate CD14 and CD44s protein expressions in tumor and normal tissues in patients with non-small cell lung cancer. Material and Methods: Thirty patients (25 males and 5 females) with non-small cell lung cancer were included in this study. Specimens obtained during the surgery were frozen in liquid nitrogen, and sliced with a thickness of 5 pm using a microtome. Standard immunohistochemical procedures were used for staining and visualization. Differences in staining patterns between normal and tumor tissues were analyzed statistically with Chi-square test.Results: CD14 and CD44s protein expressions were found both in tumor and in the normal tissues. There was no statistically significant difference in staining patterns between normal and tumor tissues (p>0.05).Conclusion: The expression of the two molecules in both tumoral and healthy tissues demonstrates that different pathways of tumor immunity affect the prognosis of the patients. However, further studies are needed in different types of cancers with larger numbers of cases and different antibodies are needed to clarify the role of CD14 and CD44s

Tumor apelin immunoreactivity is correlated with body mass index in ovarian high grade serous carcinoma

Ovarian cancer has a high mortality rate. Serous carcinoma is the most common subtype and can be detected by distant or lymph node metastasis in advanced stages. Apelin, an adipokine associated with obesity, and its receptor, APJ, participate in lymphatic invasion. Angiogenesis also can affect lymph node involvement in serous ovarian carcinomas. We investigated apelin/APJ receptor immunoreactivity in stages III and IV ovarian cancer with or without lymph node involvement and correlated the results with body mass index (BMI) to determine whether the potential relation of the two affects the outcome of the cancer. We investigated 30 patients diagnosed between 2014 and 2016 with high grade serous ovarian cancer. Tumor:stroma ratio, indirect immunoperoxidase method, H-score and MATLAB analysis were performed. In obese and pre-obese patients, tumor apelin immunoreactivity was stronger than for patients with normal BMI. Tumor:stroma ratio was correlated with survival and lymph node involvement. Strong apelin and moderate APJ immunoreactivity was detected in both lymph node negative and positive patients. BMI was related to both survival outcome and apelin immunoreactivity. BMI, adipokines such as apelin, and the stromal compartment play critical roles in advanced stage serous carcinomas