Structure and Function in Early Glaucoma

Glaucoma is a group of diseases, which exhibit a characteristic optic neuropathy and may result in progressive visual field loss. The most important risk factor is raised intraocular pressure (IOP) usually secondary to reduced aqueous outflow through the anterior chamber angle. It is the second leading cause of blindness globally. The diagnosis of glaucoma is difficult, as there is currently no widely-accepted “clinical standard” for diagnosis, although “progressive structural optic nerve and/or nerve fiber layer damage” is currently the most commonly accepted diagnostic criterion. Current treatments are to reduce the level of IOP, either by topical medication or surgery. Unfortunately, medical intervention frequently takes place after visual field loss has occurred. Consequently, much effort has been placed into the early diagnosis of glaucoma, in order to prevent damage. Visual field tests have been a popular clinical method to determine functional defects, and they are essential for managing and diagnosing glaucoma. Various methods and test strategies have been developed. Computerized threshold static perimetry involves determining the dimmest stimulus that can be seen at a number of pre-determined test point locations. An examiner can interpret the resulting pattern of defect; also, disease progress can be followed over time. Visual fields should not be interpreted in isolation but in conjunction with other clinical findings1. Standard automated perimetry (SAP) is our oldest and best documented, computerized, subjective visual function test. Threshold tests are commonly used for both detection and follow-up of glaucoma patients. Different testing strategies and different stimuli have been developed with expectations of raising the sensitivity for early detection of glaucoma-related functional change, such as short wavelength automated perimetry (SWAP), high-pass resolution perimetry (HRP), frequency doubling technology (FDT) and Flicker Defined Form (FDF). FDF is a temporally driven illusion in which background elements and stimulus elements are flickered in counterphase at a high temporal frequency, creating an illusory contour at the boundary between the background and the stimulus. It has been described to be a predominantly magnocellular-based stimulus due to its dependence on high temporal frequencies and its perceived low spatial frequency. The random flickering dots throughout the field of view and the complex nature of the stimulus, a phase-difference percept requiring higher order processing. Clinically, besides testing for deficits in function, measuring of retinal structure plays an important role in the diagnosis of early glaucoma. Damage results in characteristic signs in the retinal nerve fiber layer, the parapapillary retina and the optic nerve head, due to the oriented distribution of the nerve fiber in the retina. Scanning laser tomography (SLT; Heidelberg Retina Tomograph, Heidelberg, Germany) is a confocal scanning laser device that provides accurate and reproducible topographical information of the optic disc and peripapillary retina. Other methods such as optic disc photography, retinal nerve fiber layer photography, scanning laser polarimetry, and optical cohererence tomography are also designed to detect structural changes. By analyzing the neuroretinal rim within the optic disc, the SLT provides evidence of glaucoma related structural change, such as changes in the cup to disc ratio and notching and narrowing of the neuroretinal rim. Measurements were affected by age, but it is fairly robust to astigmatism and working distance. Studies have shown correlation between visual field test results and optic nerve head structural measurements. The correlation analysis of structure and function was performed to evaluate the spatial relationship. It has been proposed that both structural and functional diagnostic methods have unique value, but the combination of methods might provide early evidence for glaucoma diagnosis and management. The objectives of this thesis are: 1. To determine the normal sensitivity and confidence limits for FDF perimetry as a function of age; 2. To determine the test-retest repeatability of FDF perimetry for stable glaucoma; and 3. To investigate the structure function relationship in glaucoma using FDF perimetry and the HRT. Normative data for different perimeters are well established. It is critical to establish normal sensitivity for the FDF perimetry. Age related sensitivity loss throughout the visual field has been previously reported. Confidence limits for normality will be established in this thesis, as only then can we examine the ability of the new clinical test to detect early glaucoma. Measures of function and structure are both relevant and required for the early diagnosis of glaucoma. The relationship between the points tested in the visual field and corresponding positions at the optic nerve head have been previously described. Comparing the FDF perimetry results with the HRT optic nerve head results has the potential to be of significant value in the diagnosis of glaucoma

Controlled actuation of liquid marbles on a dielectric

Motivated by the great potential of droplet microreactors for chemical and biological applications, a general and robust method utilizing an electric field is developed for sustained, directional and two-dimensional manipulation of nonwetting droplets (termed “liquid marbles”). With the understanding of the mechanism of actuation, this method allows individual liquid marbles to be actuated and coalesced on demand by fine-tuning the driving voltage. Moreover, in our system, cross-contamination between marbles during manipulation is avoided as confirmed by the absence of any trace DNA after amplification using a loop-mediated isothermal amplification reaction

The Hot and Clumpy Molecular Cocoon Surrounding the Ultracompact HII Region G5.89-0.39

We present observations of CH3CN (12-11) emission at a resolution of 2" toward the shell-like ultracompact HII region G5.89-0.39 with the Submillimeter Array. The integrated CH3CN emission reveals dense and hot molecular cocoon in the periphery of the HII region G5.89-0.39, with a CH3CN deficient region roughly centered at G5.89-0.39. By analyzing the CH3CN emission using population diagram analysis, we find, for the first time, a decreasing temperature structure from 150 to 40 K with the projected distance from Feldt's star, which is thought to be responsible for powering the HII region. Our results further indicate that the majority of the heating energy in the observed dense gas is supplied by the Feldt's star. From the derived CH3CN column density profile, we conclude that the dense gas is not uniformly-distributed but centrally-concentrated, with a power-law exponent of 5.5 for r < 8000 AU, and 2.0 for 8000 AU < r < 20000 AU, where r is the distance to Feldt's star. The estimated large power index of 5.5 can be attributed to an enhancement of CH3CN abundance in the close vicinity of Feldt's star.Comment: accepted for publication in The Astrophysical Journal Letter

Budding-like division of all-aqueous emulsion droplets modulated by networks of protein nanofibrils.

Networks of natural protein nanofibrils, such as cytoskeletal filaments, control the shape and the division of cells, yet mimicking this functionality in a synthetic setting has proved challenging. Here, we demonstrate that artificial networks of protein nanofibrils can induce controlled deformation and division of all-aqueous emulsion droplets with budding-like morphologies. We show that this process is driven by the difference in the immersional wetting energy of the nanofibril network, and that both the size and the number of the daughter droplets formed during division can be controlled by modulating the fibril concentration and the chemical properties of the fibril network. Our results demonstrate a route for achieving biomimetic division with synthetic self-assembling fibrils and offer an engineered approach to regulate the morphology of protein gels

A Uniformly Selected Sample of Low-mass Black Holes in Seyfert 1 Galaxies

We have conducted a systematic search of low-mass black holes (BHs) in active galactic nuclei (AGNs) with broad Halpha emission lines, aiming at building a homogeneous sample that is more complete than previous ones for fainter, less highly accreting sources. For this purpose, we developed a set of elaborate, automated selection procedures and applied it uniformly to the Fourth Data Release of the Sloan Digital Sky Survey. Special attention is given to AGN--galaxy spectral decomposition and emission-line deblending. We define a sample of 309 type 1 AGNs with BH masses in the range $8 \times 10^4$--$2 \times 10^6$ \msun (with a median of $1.2 \times 10^6$ solar mass), using the virial mass estimator based on the broad Halpha line. About half of our sample of low-mass BHs differs from that of Greene & Ho, with 61 of them discovered here for the first time. Our new sample picks up more AGNs with low accretion rates: the Eddington ratios of the present sample range from $<~0.01$ to ~1, with 30% below 0.1. This suggests that a significant fraction of low-mass BHs in the local Universe are accreting at low rates. The host galaxies of the low-mass BHs have luminosities similar to those of $L^*$ field galaxies, optical colors of Sbc spirals, and stellar spectral features consistent with a continuous star formation history with a mean stellar age of less than 1 Gyr.Comment: Accepted for publication in Ap

Metal-Enriched Outflows in the Ultra-Luminous infrared Quasar Q1321+058

Quasar outflows may play important role in the evolution of its host galaxy and central black hole. In this paper, we present a detailed study of multiple outflows in the obscured ultra-luminous infrared quasar Q1321+058. The outflows reveal themselves in the complex optical and UV emission line spectrum, with a broad component blueshifted by 1650 km/s and a narrow component by 360 km/s, respectively.The higher velocity component shows ever strong N III] and strong Si III], in addition to strong [O III]5007 and [Ne III]3869 emission lines, suggesting an overabundance of N and Si relative to C. The abundance pattern is consistent a fast chemical enriching process associated with a recent starburst. The outflow extends to several tens to hundred parsecs from the quasar, and covers only a very small sky. We find that the outflow with line emitting gas is energetically insufficient to remove the ISM of the host galaxy. The velocity range and the column density suggest that the outflow might be part of the low ionization broad absorption line region as seen in a small class of quasars. The optical and UV continuum is starlight-dominated and can be modelled with a young-aged (1 Myr) plus an intermediate-aged (~0.5-1 Gyr) stellar populations, suggesting a fast building of the stellar mass in the host galaxy, consistent with the starburst-type metal abundances inferred from the high velocity outflow spectrum. The broad band spectral energy distribution shows that it is an obscured quasar with its bulk emission in the middle infrared. The star formation rate, independently estimated from UV, far-infrared, and emission line luminosity, is much lower than that is required for the co-evolution of the black hole and its host spheroid.Comment: 31 pages, accepted to Ap