Self-Collimation in Planar Photonic Crystals

We analyze, in three dimensions, the dispersion properties of dielectric slabs perforated with two-dimensional photonic crystals (PCs) of square symmetry. The band diagrams are calculated for all -vectors in the first Brillouin zone, and not only along the characteristic high-symmetry directions. We have analyzed the equal-frequency contours of the first two bands, and we found that the square lattice planar photonic crystal is a good candidate for the self-collimation of light beams. We map out the group velocities for the second band of a square lattice planar PC and show that the group velocity is the highest in the region of maximum self-collimation. Such a self-collimated beam is predicted to show beating patterns due to the specific shape of the equal-frequency contours. A geometrical transformation maps the region of the first and second photonic bands where self-collimation takes place one onto the other and gives additional insights on the structural similarities of self-collimation in those two bands

Surface plasmon enhanced light-emitting diode

A method for enhancing the emission properties of light-emitting diodes, by coupling to surface plasmons, is analyzed both theoretically and experimentally. The analyzed structure consists of a semiconductor emitter layer thinner than λ/2 sandwiched between two metal films. If a periodic pattern is defined in the top semitransparent metal layer by lithography, it is possible to efficiently couple out the light emitted from the semiconductor and to simultaneously enhance the spontaneous emission rate. For the analyzed designs, we theoretically estimate extraction efficiencies as high as 37% and Purcell factors of up to 4.5. We have experimentally measured photoluminescence intensities of up to 46 times higher in fabricated structures compared to unprocessed wafers. The increased light emission is due to an increase in the efficiency and an increase in the pumping intensity resulting from trapping of pump photons within the microcavity

Photonic crystal laser sources for chemical detection

We have realized photonic crystal lasers that permit the introduction of analyte within the peak of the optical field of the lasing mode. We have explored the design compromises for developing such sensitive low-threshold spectroscopy sources, and demonstrate the operation of photonic crystal lasers in different ambient organic solutions. We show that nanocavity lasers can be used to perform spectroscopic tests on femtoliter volumes of analyte, and propose to use these lasers for high-resolution spectroscopy with single-molecule sensitivity

Methods for controlling positions of guided modes of photonic-crystal waveguides

We analyze different methods for controlling positions of guided modes of planar photonic-crystal waveguides. Methods based both on rearrangements of holes in the photonic-crystal lattice and on changes of hole sizes are presented. The ability to tune frequencies of guided modes within a frequency bandgap is necessary to achieve efficient guiding of light within a waveguide, as well as to match frequencies of eigenmodes of different photonic-crystal-based devices for the purpose of good coupling between them. We observe and explain the appearance of acceptor-type modes in donor-type waveguides

PREDICTIVE VALUE OF FETAL NUCHAL TRANSLUCENCY IN SCREENING OF CHROMOSOMAL ABERRATIONS

In search for specific early ultrasound signs that could indicate an increased risk of hereditary or acquired disorders of the fetus, scientific researches confirm the value of exceptional ultrasound findings of nuchal translucencey (NT). The aim of the study was to determine the predictive value of the diameter of fetal NT in the detection of chromosomopathy. The investigation included 317 pregnant women with monofetal pregnancies, gestational age 11-14 weeks. The control group consisted of pregnant women in whom, after amniocentesis, a regular result of fetal karyotype was obtained. The limits of physiological and pathological findings of the NT value were not determined; instead, we used the diameters of NT that were obtained in pregnant women with pathological score of amniocentesis as potentially pathological values. Mean value of NT in the control group was 1.92±0.39mm, and in the group with pathological findings of fetal karyotype it was 2.49±0.37mm, which is a statistically significant difference (p<0.05). Mean value of the rump-crown length in the control group was 64.83±8.23mm, and the group with pathological karyotype 60.12±8.48mm; gestational age in the control group was 7.10±87.40 days, and in the pathological one 85.69±3.98 days, which speaks of homogeneity of the investigated sample (p>0.05).The probability that a patient with negative NT findings be healthy is 0.97. NT sensitivity as a marker for chromosomopathy was 0.97. The rate of false positive findings was 0.027. Specificity of NT as a marker for chromosomopathy was 0.97. The probability that a patient with positive findings NT really be ill was 0.66.Valid findings of NT can be considered safe ultrasonographic markers in the assessment of absence of chromosomopathy. Pathological finding, given the low positive predictive value of NT, must be amended by other prenatal tests before a pregnant woman is advised on prenatal invasive diagnostics

Variability of major histocompatibility complex class II DQA/DQB/DRB haplotypes in the golden jackal (Canis aureus) from Serbia

Glavni sustav tkivne podudarnosti (MHC) sudjeluje u adaptivnom imunosnom odgovoru sisavaca. Veća raznolikost gena MHC omogućuje limfocitima T da prepoznaju širi spektar antigena, što u konačnici daje jedinci, ali i populaciji veću šansu za preživljavanje napada patogena. Dobar su molekularni marker za proučavanje genetičke raznolikosti vrsta i populacija zbog svoje poligenosti i polimorfnosti. Čagalj (Canis aureus) je zvijer (red Carnivora) koja pripada porodici pasa (Canidae). Istraživanja raznolikosti gena MHC kod čaglja tek su nedavno započela unatoč njegovoj širokoj rasprostranjenosti na euroazijskom i afričkom kontinentu. Cilj ovog istraživanja je određivanje raznolikosti tro-lokusnih haplotipova DQA/DQB/DRB te pojedinih lokusa skupine II sustava MHC u populaciji čagljeva iz Srbije. U ovom istraživanju na 29 uzoraka mišića čagljeva pronađeno je tri alela lokusa DQA i DQB, četiri alela lokusa DRB te šest haplotipova. Sedam je alela dosad pronađeno samo kod čaglja, a tri su trans-specijski polimorfizmi. Tri su haplotipa pronađena samo u srpskoj populaciji, a tri haplotipa su zajednička s istočnoeuropskom populacijom. Potvrđena je postavljena hipoteza djelovanja pozitivne selekcije na svim lokusima koristeći dN/dS test, odnosno omjer nesinonimnih i sinonsimnih supstitucija na nukleotidnom slijedu alela.The genes of the major histocompatibility (MHC) system takes part in the adaptive immune response in mammals. Greater diversity of MHC genes enables T lymphocytes to recognise a wider spectrum of antigens, which in turn gives the individual a greater chance of surviving a pathogen attack. They are a good molecular marker for studying genetic diversity of both species and populations because they are polygenic and polymorphic. The golden jackal (Canis aureus) is a carnivore from the dog family (Canidae). Studies of MHC gene diversity of golden jackals have only recently emerged despite its wide distribution on the Eurasian and African continent. The aim of this graduate thesis is to determine variability of three-locus DQA/DQB/DRB haplotypes and individual Class II MHC loci in golden jackals from Serbia. In this study of 29 jackal muscle samples we have found three DQA and DQB alleles, four DRB alleles and six haplotypes. Seven alleles have only been found in jackals so far, while three alleles are trans-species polymorphisms. Three haplotypes are private to the serbian populations, while three haplotypes are shared with the Eastern European population. We have confirmed the proposed hypothesis of existing positive selection on all loci using the dN/dS test, i.e. the ratio of non-synonymous and synonymous substitutions on the allelic nucleotide sequences

CONTINUITY OF THE TYCHONOFF FUNCTOR τ

Let C be a class of the inverse systems X = {Xλ, fαβ,A}. We say that a functor F is C-continuous if F(limX) is homeomorphic with lim F(X). In the present paper the continuity of Tychonoff functor τ is investigated. Section Two contains some theorems concerning the non-emptyness and w-compactness of the limit of inverse systems of w-compact spaces. Section Three is the main section. Some theorems concering C-continuity of the Tychonoff functor τ are proved, where C is a class of the inverse systems of w-compact, τ-compact, H-closed or R-clased spaces. Mathematics subjectclassification (1980): Primary 54H25, Secondary 46H4

The application of DPSIR model in analyzing the space and environmental state on Murter Island

Cilj rada je analizirati prirodne i društveno-geografske komponente otoka Murtera da bi se dobio uvid u njihova obilježja te na temelju njih procijenilo trenutno stanje okoliša i mogućnosti razvoja otoka. Za analizu prostora korišten je integralni model proučavanja stanja okoliša – DPSIR (driving forces – pressures – states – impacts – responses) koji je osmislila Europska agencija za zaštitu okoliša (EEA, 1999.). Komponente modela: pokretačke sile (D), pritisci (P), stanje (S), učinci (I) i odgovori (R) na trenutno stanje okoliša, omogućavaju analizu i sintezu uzročnih odnosa između ljudskih aktivnosti i okoliša te njihovih posljedica i mogućih odgovora na promjene okoliša. Kao glavne pokretačke sile izdvojeni su stanovništvo i turizam koji su ujedno i glavni čimbenici pritiska na prostor. Pritisak se očituje u koncentraciji stanovništva u priobalnom pojasu otoka, broju turista, količini otpada, onečišćenosti mora i plaža tijekom turističke sezone, preopterećenosti električne mreže i dr.The aim of the author has been to analyze the natural and socio-geographical components of Murter Island in order to get familiar with their characteristics which would be the basis for evaluating the current state of the environment and development possibilities of the Island. An integrated research model DPSIR (driving forces – pressures – states – impacts – responses) designed by the European Environmental Agency (EEA, 1999) was used to analyze the environment. The model consists of driving forces (D), pressures (P), states (S), impacts (I) and responses (R) on the current state of the environment, and enables the analysis and synthesis of causal relationships between human activities and environment, as well as impacts and responses to the environmental changes. Population and tourism have been selected as the main driving forces, but also as the major pressures on the environment. The pressure is reflects in the concentration of the population in the coastal zone, the number of tourists, the amount of waste, pollution of the sea and beaches during the tourist season in overloading the electrical networks et al

High quality factors and room-temperature lasing in a modified single-defect photonic crystal cavity

We propose and analyze a new photonic crystal cavity design that supports a dipole mode with a quality factor greater than 20,000. Such a high quality factor is obtained by precise tuning of the cavity length with minimal disruption of the surrounding photonic crystal. A fabrication procedure based on dry etching of InGaAsP material in HI/H2/Ar is used to demonstrate photonic crystal lasers with smooth and straight sidewalls. These room-temperature lasers concentrate optical energy in air and are suitable for use as tunable lasers and chemical sensors

Design and Fabrication of Silicon Photonic Crystal Optical Waveguides

We have designed and fabricated waveguides that incorporate two-dimensional (2-D) photonic crystal geometry for lateral confinement of light, and total internal reflection for vertical confinement. Both square and triangular photonic crystal lattices were analyzed. A three-dimensional (3-D) finite-difference time-domain (FDTD) analysis was used to find design parameters of the photonic crystal and to calculate dispersion relations for the guided modes in the waveguide structure. We have developed a new fabrication technique to define these waveguides into silicon-on-insulator material. The waveguides are suspended in air in order to improve confinement in the vertical direction and symmetry properties of the structure. High-resolution fabrication allowed us to include different types of bends and optical cavities within the waveguides