280,044 research outputs found
Enhanced light extraction by photonic quasi-crystals in GaN blue LEDs
Get PDFThe far-field profile of photonic quasi-crystal patterned and unpatterned LEDs, fabricated from commercial epitaxial substrates by electron beam lithography, has been measured prior to lapping and dicing. Emission enhancements reach a maximum of 62%, and are strongly dependent on the filling factor. Qualitative agreement is achieved between 2-D finite-difference time-domain calculations and the experimental data
Recent developments in the design and fabrication of visible photonic band gap waveguide devices
No full textIn this paper, we present the design, fabrication and initial optical testing of dielectric waveguide devices which incorporate photonic crystals with photonic band gaps (PBG) in the visible region of the spectrum. In the design of our devices we use a full three-dimensional plane wave analysis to solve the photonic band structure simultaneously with the dielectric waveguide boundary conditions for a fixed lattice and waveguide geometry. This takes into account the finite thickness of the waveguide core, and the evanescent wave in the dielectric cladding layers. Furthermore, we explain how the effective Bloch mode index can be extracted from the results. This enables us to tackle important problems associated with mode coupling between the input waveguide and guided Bloch modes within the porous PBG region, such as Fresnel reflections at the interface and up-scattering from the holes. Finally, we present the recent fabrication of quasi-periodic photonic crystals and PBG waveguide bends
Author, publisher and bookseller : a tripartite synergy in Nigerian book industry
Get PDFThis work is about the roles of Author, Publisher and Bookseller in Book development in
Nigeria. The paper started by delving into the history of Book Publishing in Nigeria after
which it proceeded by defining who an author, a publisher, and a bookseller is and
expatiated on the indispensable roles of these key actors in Nigerian Book Industry and in
the emerging Information Society. Furthermore, the various constraints to book
development were identified while the paper advised on how the Book Industry can be
further promoted in Nigeria. However, the paper concluded and made recommendations
on how the Book sector can help in enhancing scholarship in the country
Going Beyond Counting First Authors in Author Co-citation Analysis
Get PDFThe present study examines one of the fundamental aspects of author co-citation analysis (ACA) - the way co-citation
counts are defined. Co-citation counting provides the data on which all subsequent statistical analyses and mappings
are based, and we compare ACA results based on two different types of co-citation counting - the traditional type that
only counts the first one among a cited work's authors on the one hand and a non-traditional type that takes into
account the first 5 authors of a cited work on the other hand. Results indicate that the picture produced through this non-traditional author co-citation counting contains more coherent author groups and is therefore considerably clearer. However, this picture represents fewer specialties in the research field being studied than that produced through the traditional first-author co-citation counting when the same number of top-ranked authors is selected and analyzed. Reasons for these effects are discussed
Time to Build, Option Value, and Investment Decisions
Get PDFMany investment projects have the following characteristics: (i) spending decisions and cash outlays occur sequentially over time, (ii) there is a maximum rate at which outlays and construction can proceed -- it takes "time to build," and (iii) the project yields no cash return until it is actually completed. Furthermore, the pattern of investment outlays is usually flexible,and can be adjusted as new information arrives. For such projects traditional discounted cash flow criteria, which treat the spending pattern as fixed, are inadequate as a guide for project evaluation. This paper develops an explicit model of investment projects with these characteristics, and uses option pricing methods to derive optimal decision rules for investment outlays over the entire construction program. Numerical solutions are used to demonstrate how time to build, opportunity cost, and uncertainty interact in affecting the investment decision. We show that with moderate levels of uncertainty over the future value of the completed project, a simple NPV rule could lead to gross over-investment. Also, we show how the contingent nature of the investment program magnifies the depressive effect of increased uncertainty on investment spending.
Survival Trends for Uterine Sarcomas from a Tertiary Center: The Oxford Experience
Get PDF: Uterine sarcomas are rare and aggressive gynecological malignancies. We evaluated the epidemiology, treatment outcomes and survival rates in uterine sarcoma patients managed in our institute. The medical records of women with histology proven uterine sarcoma, including leiomyosarcoma (LMS), adenosarcoma (ADS), and endometrial stromal sarcoma (ESS), treated at our institution from February 2010 to February 2022, were analyzed. In total, 41 patients were identified. In detail, LMS, ADS, and high-grade and low-grade ESS were identified, respectively, in 60.9%, 19.5%, 12.1%, and 7.3% of the cases. The majority of women affected by LMS (72%) underwent primary surgery and 40% of them also received adjuvant chemotherapy. A surgical approach was the preferred mode of treatment in 83% of the recurrences. The median OS (overall survival), DFS (disease free survival), and PFS (progression free survival) for the LMS group were 25, 44.5, and 8 months, respectively. The 5-year survival rates for LMS, ADS, and ESS groups were 30.5%, 100% and 37.5%, respectively. The 5-year survival for LMS was found to be significantly worse than for other histology types (p = 0.016). Our study provides valuable data for the evaluation of treatment strategies and survival trends among these rare cancers. The management and follow-up planning of each subtype requires a thorough patient-focused multidisciplinary discussion
Computational design and microfabrication of photonic quasicrystals
No full textPhotonic crystals are attracting much interest due to their ability to inhibit spontaneous emission of light. This and related properties arise from the formation of photonic bandgaps, whereby multiple scattering of light by lattices of periodically varying refractive indices act to prevent the propagation of electromagnetic waves having certain wavelengths. The etching of regular two-dimensional vertical air rods has formed a popular method for the formation photonic crystals in a dielectric planar waveguide. However, the ability for such a structure to possess a complete photonic bandgap is only possible by the use of large air rod diameters and high dielectric constants. Such structures lead to significant losses due to refractive index mismatch and large out-of-plane scattering when coupled with current fibre optical networks of low refractive index.In this thesis the use of a quasicrystalline structure is proposed instead of the regular crystal lattice. For the first time, a twelve-fold symmetric photonic quasicrystal is designed and successfully modelled using the finite-difference time-domain method. It was shown to possess a complete and absolute photonic bandgap with small air rods in a relatively low refractive index material Silicon Nitride (n=2.02). It is also shown that such complete and absolute photonic bandgaps are also realisable in low refractive index materials such as glass (n=1.45). This would provide a whole range of optical devices based on the photonic quasicrystal that are directly compatible with current fibre optical networks.The first photonic quasicrystal embedded in a Silicon Nitride waveguide to operate in the visible to infrared region of the electromagnetic spectrum was also shown. The quasicrystal was experimentally shown to possess the complete and absolute photonic bandgap.</p
Health-Related Quality of Life after Hysterectomy for Endometrial Cancer: The Impact of Enhanced Recovery after Surgery Shifting Paradigm
Get PDFObjectives: Enhanced recovery after surgery (ERAS) protocols provide well-known benefits in the immediate recovery with a shorter length of stay (LOS) also in gynecological surgery. However, the impact of ERAS has not been clearly showed yet regarding long-term consequences and health-related quality of life (HRQL). The aim of this study is to investigate the impact of ERAS on HRQL after hysterectomy for endometrial cancer. Design: Observational retrospective study with propensity score matching (PSM). Participants We administered the SF-36 validated questionnaire to women underwent hysterectomy and lymph nodal staging before and after introducing ERAS protocol, getting, respectively, a standard practice (SP) and ERAS group Settings Academic hospital Methods We collected demographic, clinical, surgical and postoperative data and performed a PSM of the baseline coufouders. We administered the questionnaire four weeks after the surgery. The SF-36 measures HRQL using eight scales: physical functioning (PF), role physical (RLP), bodily pain (BP), general health (GH), vitality (Vt), social functioning (SF), role emotional (RLE) and mental health (MH). Results After PSM, we enrolled a total of 154 patients, 77 in each group (SP and ERA). The two groups were similar in terms of age, BMI, anaesthesiologic risk, Charlson comorbidity index (CCI) and surgical technique (minimally invasive versus open access). Median LOS was shorter for ERAS group (5 versus 3 days; p = 0.02), while no significant differences were registered in the rates of postoperative complications (16.9% versus 17.4%; p = 0.66). Response rates to SF-36 questionnaire were 89% and 92%, respectively, in SP and ERAS group. At multivariate analyzes, the mean scores of SF-36 questionnaire, registered at 28 days weeks after surgery (range 26-32 days), were significantly higher in ERAS group for PF (73.3 vs 91.6; p < 0.00), RLP (median 58.3 vs 81.2; p = 0.02) and SF (37.5 versus 58.3; p = 0.01) domains, when compared to SP patients. Limitations Further follow-up was not possible due to the anonymized data derived from clinical audit. Conclusions ERAS significantly increases HRQL of women underwent surgery for endometrial cancer. HRQL assessment should be routinary implemented in the ERAS protocol
Dispelling the Myths Behind First-author Citation Counts
Get PDFWe conducted a full-scale evaluative citation analysis study of scholars in the XML research field to explore just how different from each other author rankings resulting from different citation counting methods actually are, and to demonstrate the capability of emerging data and tools on the Web in supporting more realistic citation counting methods. Our results contest some common arguments for the continued
use of first-author citation counts in the evaluation of scholars, such as high correlations between author rankings by first-author citation counts and other citation
counting methods, and high costs of using more realistic citation counting methods that are not well-supported by the ISI databases. It is argued that increasingly available digital full text research papers make it possible for citation analysis studies to go beyond what the ISI databases have directly supported and to employ more
sophisticated methods
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