Showing papers on "Night vision published in 2010"

GaAs photovoltaics and optoelectronics using releasable multilayer epitaxial assemblies

Abstract: Although compound semiconductors like gallium arsenide have a substantial performance advantage over silicon in photovoltaic and optoelectronic applications, these do not outweigh the costly process of growing large, high-quality layers of these materials and transferring them to flexible or transparent substrates for use in devices such as solar cells, night vision cameras and wireless communication systems. But now John Rogers and his team demonstrate a new fabrication approach that may remove this disadvantage. They grow films of GaAs and AlGaAs in thick, multilayered assemblies in a single deposition sequence, then release the individual layers and distribute them over foreign substrates by printing. The technological potential of this strategy to large-area applications is illustrated with the fabrication of GaAs devices such as field-effect transistors on glass and photovoltaic modules on sheets of plastic. Although compound semiconductors like gallium arsenide (GaAs) offer advantages over silicon for photovoltaic and optoelectronic applications, these do not outweigh the costly process of growing large layers of these materials and transferring them to appropriate substrates. However, a new fabrication approach is now demonstrated: films of GaAs and AlGaAs are grown in thick, multilayered assemblies in a single sequence; the individual layers are then released and distributed over foreign substrates by printing. Compound semiconductors like gallium arsenide (GaAs) provide advantages over silicon for many applications, owing to their direct bandgaps and high electron mobilities. Examples range from efficient photovoltaic devices1,2 to radio-frequency electronics3,4 and most forms of optoelectronics5,6. However, growing large, high quality wafers of these materials, and intimately integrating them on silicon or amorphous substrates (such as glass or plastic) is expensive, which restricts their use. Here we describe materials and fabrication concepts that address many of these challenges, through the use of films of GaAs or AlGaAs grown in thick, multilayer epitaxial assemblies, then separated from each other and distributed on foreign substrates by printing. This method yields large quantities of high quality semiconductor material capable of device integration in large area formats, in a manner that also allows the wafer to be reused for additional growths. We demonstrate some capabilities of this approach with three different applications: GaAs-based metal semiconductor field effect transistors and logic gates on plates of glass, near-infrared imaging devices on wafers of silicon, and photovoltaic modules on sheets of plastic. These results illustrate the implementation of compound semiconductors such as GaAs in applications whose cost structures, formats, area coverages or modes of use are incompatible with conventional growth or integration strategies.

Nanodomain Control of Exocytosis Is Responsible for the Signaling Capability of a Retinal Ribbon Synapse

Abstract: Primary sensory circuits encode both weak and intense stimuli reliably, requiring that their synapses signal over a wide dynamic range. In the retinal circuitry subserving night vision, processes intrinsic to the rod bipolar (RB) cell presynaptic active zone (AZ) permit the RB synapse to encode signals generated by the absorption of single photons as well as by more intense stimuli. In a study using an in vitro slice preparation of the mouse retina, we provide evidence that the location of Ca channels with low open probability within nanometers of the release sites is a critical determinant of the physiological behavior of the RB synapse. This gives rise to apparent one-to-one coupling between Ca channel opening and vesicle release, allowing presynaptic potential to be encoded linearly over a wide dynamic range. Further, it permits a transition from univesicular to multivesicular release (MVR) when two Ca channels/AZ open at potentials above the threshold for exocytosis. MVR permits small presynaptic voltage changes to elicit postsynaptic responses larger than quantal synaptic noise.

Nonlinear self-filtering of noisy images via dynamical stochastic resonance

Abstract: From night vision and objects overwhelmed by sunlight to jammed signals and those that are purposely encrypted, detecting low-level or hidden signals is a fundamental problem in imaging. Here, we develop and exploit a new type of stochastic resonance, in which nonlinear coupling allows signals to grow at the expense of noise, to recover noise-hidden images propagating in a self-focusing medium. The growth rate is derived analytically by treating the signal–noise interaction as a photonic beam–plasma instability and matches experimentally measured resonances in coupling strength, noise statistics and modal content of the signal. This is the first observation of nonlinear intensity exchange between coherent and spatially incoherent light and the first demonstration of spatial coherence resonance for a dynamically evolving signal. The results suggest a general method of reconstructing images through seeded instability and confirm information limits predicted, but not yet observed, in nonlinear communications systems. By exploiting stochastic resonance — in which nonlinear coupling allows signals to grow at the expense of noise — scientists show that they can recover noise-hidden images propagating in a self-focusing medium. The findings pave the way for a variety of nonlinear instability-driven imaging techniques.

Age-Related Deterioration of Rod Vision in Mice

Abstract: Even in healthy individuals, aging leads to deterioration in visual acuity, contrast sensitivity, visual field, and dark adaptation. Little is known about the neural mechanisms that drive the age-related changes of the retina and, more specifically, photoreceptors. According to one hypothesis, the age-related deterioration in rod function is due to the limited availability of 11-cis-retinal for rod pigment formation. To determine how aging affects rod photoreceptors and to test the retinoid-deficiency hypothesis, we compared the morphological and functional properties of rods of adult and aged B6D2F1/J mice. We found that the number of rods and the length of their outer segments were significantly reduced in 2.5-year-old mice compared with 4-month-old animals. Aging also resulted in a twofold reduction in the total level of opsin in the retina. Behavioral tests revealed that scotopic visual acuity and contrast sensitivity were decreased by twofold in aged mice, and rod ERG recordings demonstrated reduced amplitudes of both a- and b-waves. Sensitivity of aged rods determined from single-cell recordings was also decreased by 1.5-fold, corresponding to not more than 1% free opsin in these photoreceptors, and kinetic parameters of dim flash response were not altered. Notably, the rate of rod dark adaptation was unaffected by age. Thus, our results argue against age-related deficiency of 11-cis-retinal in the B6D2F1/J mouse rod visual cycle. Surprisingly, the level of cellular dark noise was increased in aged rods, providing an alternative mechanism for their desensitization.

Homography normalization for robust gaze estimation in uncalibrated setups

Abstract: Homography normalization is presented as a novel gaze estimation method for uncalibrated setups. The method applies when head movements are present but without any requirements to camera calibration or geometric calibration. The method is geometrically and empirically demonstrated to be robust to head pose changes and despite being less constrained than cross-ratio methods, it consistently performs favorably by several degrees on both simulated data and data from physical setups. The physical setups include the use of off-the-shelf web cameras with infrared light (night vision) and standard cameras with and without infrared light. The benefits of homography normalization and uncalibrated setups in general are also demonstrated through obtaining gaze estimates (in the visible spectrum) using only the screen reflections on the cornea.

Wide-field motion tuning in nocturnal hawkmoths.

Abstract: Nocturnal hawkmoths are known for impressive visually guided behaviours in dim light, such as hovering while feeding from nectar-bearing flowers. This requires tight visual feedback to estimate and counter relative motion. Discrimination of low velocities, as required for stable hovering flight, is fundamentally limited by spatial resolution, yet in the evolution of eyes for nocturnal vision, maintenance of high spatial acuity compromises absolute sensitivity. To investigate these trade-offs, we compared responses of wide-field motion-sensitive neurons in three species of hawkmoth: Manduca sexta (a crepuscular hoverer), Deilephila elpenor (a fully nocturnal hoverer) and Acherontia atropos (a fully nocturnal hawkmoth that does not hover as it feeds uniquely from honey in bees' nests). We show that despite smaller eyes, the motion pathway of D. elpenor is tuned to higher spatial frequencies and lower temporal frequencies than A. atropos, consistent with D. elpenor's need to detect low velocities for hovering. Acherontia atropos, however, presumably evolved low-light sensitivity without sacrificing temporal acuity. Manduca sexta, active at higher light levels, is tuned to the highest spatial frequencies of the three and temporal frequencies comparable with A. atropos. This yields similar tuning to low velocities as in D. elpenor, but with the advantage of shorter neural delays in processing motion.

Melatonin potentiates glycine currents through a PLC/PKC signalling pathway in rat retinal ganglion cells

Abstract: In vertebrate retina, melatonin regulates various physiological functions. In this work we investigated the mechanisms underlying melatonin-induced potentiation of glycine currents in rat retinal ganglion cells (RGCs). Immunofluorescence double labelling showed that rat RGCs were solely immunoreactive to melatonin MT(2) receptors. Melatonin potentiated glycine currents of RGCs, which was reversed by the MT(2) receptor antagonist 4-P-PDOT. The melatonin effect was blocked by intracellular dialysis of GDP-beta-S. Either preincubation with pertussis toxin or application of the phosphatidylcholine (PC)-specific phospholipase C (PLC) inhibitor D609, but not the phosphatidylinositol (PI)-PLC inhibitor U73122, blocked the melatonin effect. The protein kinase C (PKC) activator PMA potentiated the glycine currents and in the presence of PMA melatonin failed to cause further potentiation of the currents, whereas application of the PKC inhibitor bisindolylmaleimide IV abolished the melatonin-induced potentiation. The melatonin effect persisted when [Ca(2+)](i) was chelated by BAPTA, and melatonin induced no increase in [Ca(2+)](i). Neither cAMP-PKA nor cGMP-PKG signalling pathways seemed to be involved because 8-Br-cAMP or 8-Br-cGMP failed to cause potentiation of the glycine currents and both the PKA inhibitor H-89 and the PKG inhibitor KT5823 did not block the melatonin-induced potentiation. In consequence, a distinct PC-PLC/PKC signalling pathway, following the activation of G(i/o)-coupled MT(2) receptors, is most likely responsible for the melatonin-induced potentiation of glycine currents of rat RGCs. Furthermore, in rat retinal slices melatonin potentiated light-evoked glycine receptor-mediated inhibitory postsynaptic currents in RGCs. These results suggest that melatonin, being at higher levels at night, may help animals to detect positive or negative contrast in night vision by modulating inhibitory signals largely mediated by glycinergic amacrine cells in the inner retina.

Pedestrian detection in near-infrared night vision system

Abstract: Several premium automotive brands offer night vision systems to enhance the driver's ability to see at night. Most recent generation night vision systems have added pedestrian detection as a feature to assist drivers to avoid potential collisions. This paper reviews pedestrian detection based on two different sensing technologies: active night vision operating in the near-infrared (NIR) region of the electromagnetic spectrum, and passive night vision operating in the far-infrared (FIR) spectrum. It also discusses the pros and cons of each type of night-vision system with-respect-to the pedestrian detection capability, the effectiveness for collision avoidance, and the commercial attractiveness. The paper introduces an enhancement to the NIR active lighting scheme that significantly improves the pedestrian detection performance. With improved pedestrian detection performance, we argue that the NIR night vision system is more effective at improving night-time driving safety and may achieve broader market acceptance.

Fine-mapping and mutation analysis of TRPM1: a candidate gene for leopard complex (LP) spotting and congenital stationary night blindness in horses

Abstract: Leopard Complex spotting occurs in several breeds of horses and is caused by an incompletely dominant allele (LP). Homozygosity for LP is also associated with congenital stationary night blindness (CSNB) in Appaloosa horses. Previously, LP was mapped to a 6 cm region on ECA1 containing the candidate gene TRPM1 (Transient Receptor Potential Cation Channel, Subfamily M, Member 1) and decreased expression of this gene, measured by qRT-PCR, was identified as the likely cause of both spotting and ocular phenotypes. This study describes investigations for a mutation causing or associated with the Leopard Complex and CSNB phenotype in horses. Re-sequencing of the gene and associated splice sites within the 105 624 bp genomic region of TRPM1 led to the discovery of 18 SNPs. Most of the SNPs did not have a predictive value for the presence of LP. However, one SNP (ECA1:108,249,293 C>T) found within intron 11 had a strong (P < 0.0005), but not complete, association with LP and CSNB and thus is a good marker but unlikely to be causative. To further localize the association, 70 SNPs spanning over two Mb including the TRPM1 gene were genotyped in 192 horses from three different breeds segregating for LP. A single 173 kb haplotype associated with LP and CSNB (ECA1: 108,197,355- 108,370,150) was identified. Illumina sequencing of 300 kb surrounding this haplotype revealed 57 SNP variants. Based on their localization within expressed sequences or regions of high sequence conservation across mammals, six of these SNPs were considered to be the most likely candidate mutations. While the precise function of TRPM1 remains to be elucidated, this work solidifies its functional role in both pigmentation and night vision. Further, this work has identified several potential regulatory elements of the TRPM1 gene that should be investigated further in this and other species.

Insights into the adaptive significance of vertical pupil shape in snakes

Abstract: Pupil shape in vertebrates ranges from circular to vertical, with multiple phylogenetic shifts in this trait. Our analyses challenge the widely held view that the vertical pupil evolved as an adaptation to enhance night vision. On functional grounds, a variable-aperture vertical pupil (i) allows a nocturnal species to have a sensitive retina for night vision but avoid dazzle by day by adjusting pupil closure, and (ii) increases visual acuity by day, because a narrow vertical pupil can project a sharper image onto the retina in the horizontal plane. Detection of horizontal movement may be critical for predators that wait in ambush for moving prey, suggesting that foraging mode (ambush predation) as well as polyphasic activity may favour the evolution of vertical pupil shape. Camouflage (disruption of the circular outline of the eye) also may be beneficial for ambush predators. A comparative analysis in snakes reveals significant functional links between pupil shape and foraging mode, as well as between pupil shape and diel timing of activity. Similar associations between ambush predation and vertically slit pupils occur in lizards and mammals also, suggesting that foraging mode has exerted major selective forces on visual systems in vertebrates.

Variation of spectral response for exponential-doped transmission-mode GaAs photocathodes in the preparation process.

Abstract: To confirm the actual effect of an exponential-doped structure on cathode performance, an exponential-doped structure was applied to the preparation of a transmission-mode GaAs photocathode, and spectral response curves after high-temperature activation, low-temperature activation, and the indium sealing process were separately measured by use of the on-line spectral response measurement system The results show that, compared to the previously uniform-doped photocathode, the exponential-doped photocathode can obtain higher cathode performance and photoemission capability because of the built-in electric field Nevertheless, cesium desorption and impurity of gas during the sealing process can cause the degeneration of spectral response in the entire response waveband, especially in the long-wavelength region, with the decrease in surface electron escape probability related to the adverse evolution of the surface potential barrier profile

Investigation of Driver Performance With Night Vision and Pedestrian Detection Systems—Part I: Empirical Study on Visual Clutter and Glance Behavior

Abstract: This paper describes two studies in which two night-vision enhancement systems were examined to compare nighttime driver performance in pedestrian detection. In the first study, the levels of clutter in the images displayed by the two types of night-vision enhancement systems were measured objectively and subjectively. The subjective ratings of clutter changed as a power function of the objective measure of clutter intensity. In the second study, the effect of clutter on glance behavior during pedestrian detection was examined in a driving simulator. Night-vision images with less clutter required shorter search times and fewer glances to detect the pedestrian, but the duration of each glance remained relatively constant.

Infrared night-vision zoom camera mobile phone

Abstract: The utility model provides an infrared night-vision zoom camera mobile phone which comprises a mobile phone unit and a camera unit, wherein the camera unit is arranged inside the mobile phone unit; the camera unit is an infrared night-vision camera and comprises an image pick-up module; and the image pick-up module comprises a focal length-variable camera, a light-filtering module and a focal length adjustor. The light-filtering module allows the infrared night-vision zoom camera mobile phone to take pictures normally under the condition of insufficient lighting or lack of lighting. In addition, the focal length adjustor is arranged to regulate the definition of the image to be picked up when taking pictures. The infrared night-vision zoom camera mobile phone solves the defect that the traditional mobile phone fails to take pictures at night or under insufficient lighting condition.

Spectral-domain optical coherence tomography and fundus autofluorescence characteristics in patients with fundus albipunctatus and retinitis punctata albescens.

Abstract: Purpose: Fundus albipunctatus is a form of congenital stationary night blindness characterized by an early onset and nonprogressive impairment of night vision and the presence of numerous dull-white punctate lesions scattered throughout the fundus, while retinitis punctata albescens patients often show similar fundus changes but manifest a severe and progressive hereditary retinal dystrophy.Conclusions: In this study, we report the optical coherence tomography and fundus autofluorescence measurements in patients with these hereditary night blinding diseases.

Rail for inductively powering firearm accessories

Abstract: A method and system for an inductively powering rail on a firearm to power accessories such as: telescopic sights, tactical sights, laser sighting modules, and night vision scopes. This is achieved by having primary and secondary electromagnets (U-Cores) on both the inductively powering rail and the accessory. Once the electromagnets are in contact, the accessory is able to obtain power through induction via the inductively powering rail. Accessories may be attached to various fixture points on the inductively powering rail and are detected by the firearm when attached and detached. When attached, power and data communications may flow between the accessory and a master CPU located on the firearm. Accessories that are attached to the inductively powering rail and have rechargeable power systems may be recharged via the inductive power rail. Further, accessories that have power that is not needed may be transferred to other accessories.

The effect of presbyopic vision corrections on nighttime driving performance

Abstract: Purpose. To investigate the effect of various presbyopic vision corrections on night-time driving performance on a closed road driving circuit. Methods. Participants included 11 presbyopes (mean age: 57.3+/-5.8 years), with a mean best sphere distance refractive error of R+0.23+/-1.53 DS; L+0.20+/-1.50 DS, whose only experience of wearing presbyopic vision corrections was reading spectacles. The study involved a repeated measures design, where participant's night-time driving performance was assessed on a closed road circuit when wearing each of four power-matched vision corrections. These included single vision distance lenses (SV), progressive addition spectacle lenses (PAL), monovision contact lenses (MV) and multifocal contact lenses (MTF CL) worn in a randomized order. Measures included low contrast road hazard detection and avoidance, road sign and near target recognition, lane-keeping, driving time and legibility distance for street signs. Eye movement data (fixation duration and number of fixations) were also recorded. Results. Street sign legibility distances were shorter when wearing MV and MTF CL than SV and PAL (p Language: en

Physical insight into light scattering by photoreceptor cell nuclei

Abstract: A recent study showed that the rod photoreceptor cell nuclei in the retina of nocturnal and diurnal mammals differ considerably in architecture: the location of euchromatin and heterochromatin in the nucleus is interchanged. This inversion has significant implications for the refractive index distribution and the light scattering properties of the nucleus. Here, we extend previous two-dimensional analysis to three dimensions (3D) by using both a numerical finite-difference time-domain and an analytic Mie theory approach. We find that the specific arrangement of the chromatin phases in the nuclear core-shell models employed have little impact on the far-field scattering cross section. However, scattering in the near field, which is the relevant regime inside the retina, shows a significant difference between the two architectures. The "inverted" photoreceptor cell nuclei of nocturnal mammals act as collection lenses, with the lensing effect being much more pronounced in 3D than in two dimensions. This lensing helps to deliver light efficiently to the light-sensing outer segments of the rod photoreceptor cells and thereby improve night vision.

Electrical connector including a bayonet locking device

Abstract: An electrical connector for a helmet-mounted night vision system, or other electronic device, is provided. The electrical connector includes a plug assembly and a receptacle assembly each including a body having a revolved surface and an electrical contact. A protrusion extends from the revolved surface of either the plug assembly or the receptacle assembly and a cam surface is defined along the revolved surface of the other of the plug assembly and the receptacle assembly. Upon engagement between the assemblies, the revolved surfaces of the assemblies are positioned to face each other and upon rotation of the assemblies with respect to one another the protrusion is positioned to move along the cam surface causing the electrical contact of the plug assembly to bear against the electrical contact of the receptacle assembly thereby establishing a connection between the plug assembly and the receptacle assembly.

A novel day blindness in sheep: epidemiological, behavioural, electrophysiological and histopathological studies

Abstract: Four genetically related Improved Awassi sheep flocks had sporadic births of lambs with congenital visual impairments that differed from other known forms of sheep blindness. Pedigree analysis suggested an autosomal recessive mode of inheritance. Behavioural studies of 4-month old affected lambs showed that their day vision (but not night vision) was impaired. Electrophysiological results at this age demonstrated diminished function of cones but not rods. Histopathological and immunohistochemical evaluation of affected retinas from 5-month old lambs revealed both red-green and blue cones, suggesting that the behavioural day blindness and reduced cone electroretinograms reflect cone dysfunction rather than severe cone photoreceptor loss. Awassi day blindness may be a form of achromatopsia.

ALARIC Forward-Looking Ground Penetrating Radar system with standoff capability

Abstract: The use of low-frequency, ultra-wideband (UWB) radar technology to help detect concealed or buried targets has been demonstrated in the past, and could provide an important capability for combat systems on the battlefield. As part of Army's mission and technical objective, the Night Vision and Electronic Sensors Directorate, Countermine Division has designed and developed a Forward-Looking Ground-Penetrating Radar (FLGPR) with standoff capability. The forward-looking GPR is an impulse-based radar system with a bandwidth that spans between 300 – 3000 MHz. The innovative design uses commercially available, off-the shelf (COTS) components to create an effective sampling scheme of approximately 8 GHz. The design is modular, and can be scaled to provide a means for future improvement of electronic components to eventually meet the requirements of various combat systems. Early results from recent tests suggest that metallic targets buried near the surface can be detected with this radar system.

Circadian variation in the electroretinogram and the presence of central melatonin

Abstract: The light/dark cycle is the most important circadian clock synchronizer for mammals and humans. Circadian rhythms of dopamine and melatonin production in the retina have been reported to follow the light and dark cycle, but their impact on rod and cone functioning is not clear. The purpose of this study was to assess diurnal variations (morning vs. evening) in retinal function as measured with the photopic and scotopic electroretinogram (ERG). We also tried to correlate our results with the presence or absence of melatonin secretion in the saliva. Photopic and scotopic luminance-response functions were obtained in 29 participants at 11:00 (when melatonin should not be present) and 23:00 (when melatonin should be present). From the luminance-response function, Vmax, log K and slope parameters were derived. In scotopic condition, a significant increase of 6% in Vmax amplitude was observed in evening compared to morning (P = 0.03) along with a prolonged b-wave implicit time of 8% (P = 0.01) and an increase in rod sensitivity in evening compared to morning (P = 0.02). As expected, these changes in rod function were accompanied by a higher concentration of melatonin in saliva samples in the evening (P = 0.01). In photopic condition, only a prolonged a-wave implicit time of 5% was observed in evening when compared to morning (P = 0.02). Our findings suggest that the rod system is favored during night time, when circulating melatonin is present. Although statistically significant changes were observed, the day vs. night difference observed in the present study appears to be too small to impact significantly upon clinical assessment of retinal function.

A frameshift mutation in SANS results in atypical Usher syndrome.

Abstract: Usher syndrome is an autosomal, recessively inherited disorder involving progressive retinitis pigmentosa and hearing loss with or without vestibular dysfunction. Usher type I (USH1) is the severest form (1). It involves profound deafness, vestibular areflexia and onset of retinitis pigmentosa in early childhood (1). To date seven genetic loci for USH1 have been mapped (USH1B-USH1H) and five of the genes have been identified. USH1G (MIM #606943) is associated with mutations in SANS (2). The encoded 461 amino acid protein, SANS, is predicted to have three ankyrin-like domains, a PDZ binding motif and a Sterile alpha motif (SAM) domain (2). SANS is expressed in many tissues including the inner ear and retina (2, 3). Jackson shaker (js) mice have a mutation in Sans. They exhibit disorganized stereocilia and are profoundly deaf, but do not exhibit a retinal phenotype (3). USH1G appears to be a rare cause of USH1 as only five mutations in SANS have been reported to cause Usher syndrome in four families (2, 4, 5) (Table 1). All mutations, except one, cause classic symptoms of USH1. A mutation in exon 2 substituting p.V458D in SANS is associated with atypical Usher syndrome. It is therefore hypothesized that missense mutations in SANS may result in hypomorphic alleles and cause a less severe phenotype as compared to frameshift mutations (4). Table 1 List of all mutations in SANS We report a consanguineous family with four affected individuals with moderate to severe hearing loss, mild retinitis pigmentosa and normal vestibular function, a phenotype which resembles an USH2 diagnosis (1). Family HLRB12 (Fig. 1a) was recruited from Sheikhupura, Pakistan with Institutional Review Board approval at University of the Punjab, and written informed consent was obtained from all participants. Three affected children were subjected to audiometric examinations at the age of 12, 14 and 21 years, in ambient noise conditions. Clinical examination revealed moderate to severe hearing loss (Fig. 1b). Vestibular function was evaluated by Romberg and tandem gait tests. Additionally, inquiries were made about whether affected children felt insecure while walking in darkness or had motion sickness. There was no delay in independent ambulation and none of the affected individuals had difficulty with balance suggesting vestibular function was normal. Additionally, none of the patients reported problems with eyesight including night vision. However, funduscopy revealed mild symptoms of retinitis pigmentosa in three of the older affected individuals examined at 5, 13, 15, and 22 years respectively. No bone spicules were observed in the retinal epithelium (Fig. 1d). The optic discs were pale as compared to those in normal individuals. Electroretinography could not be performed. Optical testing revealed a mild loss of near sight vision, which was not noted by the patients. Figure 1 (a) Pedigree of family HLRB12. Haplotypes for two closest markers to SANS are shown for the genotyped members. Alleles of the two markers were homozygous for all affected individuals. The ancestral chromosome with the SANS mutation is shaded in gray (b) ... Genotyping with fluorescently labeled markers for linkage analyses excluded all Usher syndrome loci except USH1G. Markers D17S1807 and D17S1301 lie close to SANS and showed homozygosity by descent in all affected individuals of family HLRB12 (Fig. 1a). Using a disease allele frequency of 0.001 and coding the phenotype as a fully penetrant autosomal recessive disorder, maximum two-point LOD scores of 4.2 and 3.9 were obtained at recombination fraction θ = 0 with the markers D17S1807 and D17S1301 respectively. We PCR amplified and sequenced the three exons and flanking intronic regions of SANS. In the DNA of affected individuals of family HLRB12 we identified a homozygous 15bp deletion (c.163_164+13del15) involving nucleotides in the first exon and intron of SANS (Fig. 1c, e). We did not detect this mutation in 200 chromosomes from ethnically matched controls assayed by Tetra primers ARMS PCR (6). In order to identify the effect of c.163_164+13del15 on the SANS transcript, we obtained RNA from whole blood and generated cDNA. However we found that SANS is not expressed sufficiently in blood samples (data not shown). Usually mutations that delete donor splice sites in first exons result in retention of the following introns or use of a cryptic splice site within the affected exons or introns (7, 8) . Indeed, in silico analysis for cryptic splice sites in wild type and mutant genomic sequences of SANS with GeneSplicer (http://cbcb.umd.edu/software/GeneSplicer/gene_spl.shtml) predicted retention of the first intron of in the RNA resulting from mutant, but not from the normal, SANS genomic sequence (data not shown). The retention of the first intron will introduce a frameshift and a premature stop codon in the SANS open reading frame. The presence of premature stop codons are known to mark some mRNAs for nonsense mediated decay (9) and it is possible that no mutant mRNA will be produced in patients with the deletion mutation. However, if the mRNA escapes this surveillance mechanism, the frameshift will result in a truncated nonfunctional protein of 58 amino acids. Our work indicates that both missense and deletion mutations in SANS can result in atypical Usher syndrome. Thus the location or type of mutation does not predict the severity of the disorder and the phenotypic course can be modified by unknown genetic or epigenetic factors. Furthermore, some patients with no mutations in genes which cause USH2 may have mutations in SANS.

Design of achromatic and apochromatic plastic micro-objectives

Abstract: The possibility and the efficiency of using a single diffractive lens to achromatize and apochromatize micro-objectives with plastic lenses are shown. In addition, recommendations are given on assembling the starting configurations of the objectives and calculating the design parameters required for subsequent optimization. It is also shown that achievable optical performance of achromatic and apochromatic micro-objectives with plastic lenses satisfy the qualifying standards for cell-phone objectives and closed-circuit television (CCTV) cameras.