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PubMed2006

Silicon-on-insulator irregular waveguide mode converters.

Irregular waveguide elements in a silicon-on-insulator platform that allow new device concepts are introduced. Specific designs are achieved using a multiresolution optimization strategy where the waveguide width is varied in stepwise increments. Simulation results are given for high-efficiency waveguide mode converters, power splitters, and waveguide transitions operating at 1.55 microm. The degrees of freedom available permit these functions and small dimensions, making these devices candidates for optical integrated circuits.

Journal Article↗

PubMed2006

Low-frequency fluctuations in two-state quantum dot lasers.

We study the feedback-induced instabilities in a quantum dot semiconductor laser emitting in both ground and excited states. Without optical feedback the device exhibits dynamics corresponding to antiphase fluctuations between ground and excited states, while the total output power remains constant. The introduction of feedback leads to power dropouts in the ground state and intensity bursts in the excited state, resulting in a practically constant total output power.

Journal Article↗

PubMed2003

[Early therapeutic trials for retinitis pigmentosa].

Non syndromic forms of Retinitis Pigmentosa (RP) constitute a collection of clinically and genetically heterogeneous inherited retinal degenerative diseases. They are characterized by a bilateral progressive visual loss susceptible to cause blindness. These diseases are transmitted through pedigrees according to all known modes of inheritance. They are bilateral and usually start during infancy. However, very early clinical presentations exist, such as those observed in children affected by Leber Congenital Amaurosis, as well as late onset autosomal dominant forms of retinitis pigmentosa. The characteristic clinical aspect of the rod-cone RP dystrophies is marked by alterations of the peripheral retina associated with a night blindness and a progressive narrowing of the visual field. The ophthalmoscopic examination of RP patients commonly reveals thin retinal arteries and scattered pigmentary accumulations. In contrast, there are cone rod retinal dystrophies whose onset is marked by a decreased visual acuity before the appearance of any visual field alteration. Some forms of RPs display an ocular fundus devoid of any pigmentary alteration. Syndromic forms of RPs are not uncommon. The association of deafness with RP is detected in nearly 30% of the patients. Other associations with RP can include mental deficiency, facial dysmorphy, microcephaly, obesity, kidney deficiency, immune deficiencies, metabolic disorders. The existence of such syndromic forms of RP localizes RPs at the crossroad of several medical specialties. A long lasting collaboration between our department of ophthalmology and the department of medical genetics of the Necker-Sick Children Hospital has allowed us to establish numerous genotype-phenotype correlations, especially in LCA and Stargardt's disease. ABCR gene mutations cause Stargardt disease. ABCR mutations may also cause some types of Ages Related Macular Degenerations (AMD). Nowadays, there is no known efficient therapy available for patients affected by RP. Gene therapies hold promises of treatment for patients affected by some of these diseases for the next decade. In a not too far future, the use of pharmacological drugs increasing a better intracellular oxygen availability, without triggering any harmful production of free radical oxygen species (ROS), while exerting an anti-apoptotic effect within photoreceptor cells, appears to be a therapeutical strategy deserving to be tested in an appropriately designed clinical trial. For the present time, optical and electronical devices as well as night-vision glasses are the only possible tools allowing to improve the quality of life of some patients.

Genetic Therapy↗

PubMed2006

Non-ionising radiation human exposure assessment near telecommunication devices in Croatia.

This paper gives an overview of the regulatory acts in non-ionising radiation in the world, with a special emphasis on basic guidelines issued by the International Commission on Non-Ionizing Radiation Protection (ICNIRP). ICNIRP Guidelines are implemented in many countries worldwide. Croatia has also implemented them indirectly through the European Recommendation 1999/519/EC. The Croatian regulatory acts include the Non-lonising Radiation Protection Act, Ordinance on Electromagnetic Fields (EMF) Protection, and the Ordinance on Basic Requirements for Devices which produce Optical Radiation and Measures for Optical Radiation Protection. Dosimetry and densitometry are compliant with relevant international and European standards. The paper presents an example of densitometric human exposure assessment in complex indoor exposure conditions. In spite of a high number of indoor and outdoor sources and the "worst-case exposure assessment", the results are within the limits defined by the Croatian EMF Ordinance.

Electromagnetic Fields↗

PubMed1990

Methods for the assessment of the effects of topical retinoic acid in photo-ageing and actinic keratoses.

Quantitative techniques for assessing the effects of tretinoin on photo-aged skin mainly involve humans, although hairless mice were used in initial studies. Ideally techniques should be non-invasive but occasionally biopsies have to be taken, especially when studying the effects of tretinoin on different skin compartments. Characteristic features of photo-aged skin, including the development of fine and coarse wrinkles, skin discoloration, rosy cheeks and telangiectasis, have been assessed subjectively using a visual analogue scale. Effects of tretinoin on wrinkle depth have been measured non-invasively by quantifying contours of silicone rubber replicas using either a mechanical tracking device or an optical technique employing an image-analysing computer. Changes in skin colour have been measured using an erythema meter and the stimulatory effect of tretinoin on blood flow has been established by laser doppler flowmetry. Skin thickness has been measured non-invasively using pulsed A-scan ultrasound which showed that tropical tretinoin increased thickness. Biopsies have also been used but no changes in the thickness of the dermal repair zone have been noted in humans, in contrast to the situation in hairless mice. Epidermal dysplasia has been measured by a visual analogue scale or by objective image analysis.

Humans↗

PubMedDate not supplied

[Roentgenologic converters for medical radioscopy].

Peculiarities of use of luminescent and semiconductor converters of X-radiation in radioscopy are examined. Characteristic features of X-ray devices (electro-optical transducers, X-ray vidicons, gas discharge and luminescent converters), based on the use of luminescent and semiconductor converters are comparatively analyzed. Estimation of X-ray image quality is given. Use of gas discharge and luminescent converters is found to be the most prospective for medical radioscopy. The aforementioned converters are distinguished by high dose sensitivity, simplicity of the construction and greater size of working field.

Equipment Design↗

PubMed1986

Computer-aided diagnosis of dermatologic disorders.

In conclusion, several computer programs have been developed to aid diagnosis in dermatology. These have used various methods to reach a diagnosis, with some earlier programs using probabilistic techniques and later programs using cognitive models. Several current trends, if they continue, would indicate that computer-assisted diagnosis may play a greater role. The growing number of physicians who own the prerequisite computing resources will probably want diagnostic software to accompany their office management and data base software. The increasing ease of use of diagnostic software, with rapid access and ease of updating, should make these programs more attractive to physicians. Some of the newer peripheral devices such as optical disks and voice input will probably make the software more interesting. Perhaps the most important factor governing the acceptance of computer diagnostic adjuncts is whether the software will provide a useful service to physicians. If these programs can be demonstrated to improve patient care, they may become commonplace in physicians' offices.

Artificial Intelligence↗

PubMed1995

The impact of age-related visual impairment on functional independence in the elderly.

Low vision is an extremely common problem in the elderly, which may have devastating consequences for functional independence and health status. It ranks only behind arthritis and heart disease as the etiology for impaired function in those over the age of 70. Macular degeneration is a leading cause of blindness and poor vision in the elderly. The central vision loss of this disorder can sometimes be postponed through laser therapy. Otherwise, the low visual state is best addressed with vision-enhancing devices, non-optical adaptive equipment, and patient education available through most occupational therapists. Referral to a low-vision rehabilitation program is sometimes needed for more comprehensive evaluation and intervention. Individual adaptation and supportive services often result in a significant improvement in function and quality of life for those elders with low vision.

Accidental Falls↗

PubMed1995

A new technique for measurements on long bones: development of a new instrument and techniques comparison.

In this paper we present a new instrument for measurements on long bones. The instrument is based on the use of a digital coordinatometer-goniometer connected to an optical collimator: such device allows angles as well as lengths to be measured. With regard to observing procedures, an innovative method for bone axis location by points has been applied. It is also possible to locate an axis using a symmetry and tangency criterion. As for torsion angles, the proposed technique is absolutely new; it utilizes a reference plane, which the bone must be leaned against, and the symmetry conditions that are generated by rotating the bone around an axis orthogonal to this plane. In order to verify the precision of the new instrument (digital osteogoniometer), several tests were performed. For this purpose we have studied the results of measurements carried out with the new instrument as well as with traditional apparatuses by four different observers on a sample of 10 skeletons (humerus, radius, ulna, femur, tibia of left side). The analysis of intrapersonal and interpersonal differences points out that the new osteogoniometer is more precise in angular measurements than traditional instruments. Moreover the time requested for carrying out measurements prooved to be shorter, above all with regard to torsion angles measurements.

Adult↗

PubMed1994

[Initial results with video-controlled pulmonary lobectomy in 6 patients in The Netherlands].

In the period from May to September 1993 six patients underwent video-assisted lobectomy of the lung. Owing to the development of video optics and endoscopic devices video-assisted lobectomy is now possible; it appears to be a promising alternative to posterolateral thoracotomy. Potential advantages of this method in comparison with posterolateral thoracotomy are: less pain and improved pulmonary function in the first 24 hours postoperatively, better preservation of shoulder girdle strength and movement, shorter recovery period and hospital stay, and a better cosmetic result. Many aspects of this new technique need further prospective investigation, however.

Aged↗

PubMed1993

[A case of multiple sclerosis associated with chronic inflammatory demyelinating polyradiculoneuropathy].

We report a 19-year-old girl with multiple sclerosis (MS) who had chronic inflammatory demyelinating polyradiculoneuropathy (CIDP). At the age of 9 (1981), she was diagnosed as having Devic disease, including optic neuritis and transverse myelitis. For two years after the onset of the disease, she suffered from three relapses of MS and was treated with prednisone. At the age of 11, she noticed muscle weakness and sensory disturbance of four limbs. On examination, all tendon reflexes were absent, CSF protein was elevated, and motor nerve conduction velocity of the ulnar nerves was markedly slowed. Sural nerve biopsy showed decreased density of myelinated fibers and de-re-myelinated fibers with onion-bulb formations. Between 11 and 19 years, she had a number of episodes of the central nervous system (CNS) and peripheral nervous system (PNS) deficits with partial or complete recovery by oral administration of prednisone. The clinical course and laboratory data are consistent with MS associated with CIDP. Such our case of MS with CIDP in childhood is very rare. Patients with MS and CIDP may represent a subpopulation who had a common pathogenetic factor for both CNS and PNS demyelination.

Adult↗

PubMedDate not supplied

Total quality in tubing glass manufacturing.

Today's demand for higher quality products can be satisfied through a comprehensive quality assurance system (Total Quality System, "Worldwide Quality Standard") using the latest state of the art measuring technologies. Totally automated state of the art glass vial manufacturing begins once the glass tubes are loaded into the machine and ends with the finished product in the packaging machine, all without human contact. This standard is achieved by measuring dimensions with SPC (statistical process control) and 100% inspection of the products. These systems complement each other and give the machine operator instant data in an overview format. To achieve the visual requirements forma vitrum developed the FVC90 control line. This optical surface inspection device controls online and without contact 100% of the products for cosmetic defects as small as 50 microns. It can detect and eject defects such as dirt, scratches, chips, air-lines, loose glass particles, cracks, etc. The sensitivity of the system can be adjusted and is fixed based on client needs. An important quality assurance technique is the checking of dimensions at the production machine with a Vision System. With this system deviations are instantly recognized and corrections can be made immediately, thus assuring that glass products can be run on the high-speed filling machines for which they are designed. These computer assisted inspection systems are key in producing the highest quality pharmaceutical glassware in the 90's.

Computer-Aided Design↗

PubMed1996

Effect of craniectomy/durotomy alone and in combination with hyperventilation, diuretics, and corticosteroids on intracranial pressure in clinically normal dogs.

OBJECTIVE: To determine the effect of craniectomy and durotomy on intracranial pressure (ICP) in clinically normal dogs. DESIGN: Two-part study (experiments A and B) involving craniectomy and durotomy, with and without treatments to lower ICP. ANIMALS: Six (experiment A) and 7 (experiment B) healthy dogs. PROCEDURE: In experiment A, craniectomy was performed in combination with durotomy, diuretic administration, methylprednisolone sodium succinate administration, and hyperventilation, and effect of these manipulations on ICP was determined. In experiment B, dogs had only craniectomy and durotomy without associated ICP-lowering treatments. During both experiments, ICP was monitored throughout the surgical procedure with a fiber optic ICP monitoring device. RESULTS: Intracranial pressure decreased after the combination of craniectomy, durotomy, and other ICP-lowering treatments in dogs of experiment A. Similar magnitude of decrease in ICP was observed in dogs of experiment B after craniectomy and durotomy. CONCLUSIONS: Comparison of these experiments indicate that surgical removal of overlying skull and incision of the dura mater can significantly decrease ICP in clinically normal dogs. CLINICAL RELEVANCE: Craniectomy and durotomy may be useful as an adjunct treatment for increased ICP.

Adrenal Cortex Hormones↗

PubMed1996

[Subjective contrast evaluation by visually handicapped patients].

Personal optical and electronic devices are helpful to people with binocular vision of less than 0.3 or a substantially impaired visual field. Striking brightness and color contrast may help patients to orient themselves outdoors. This is particularly true for patients with age-related macular degeneration who have diminished contrast sensitivity as evaluated by the Vistech test and the low-contrast sensitivity test. In this study, the desired level or color combination of contrasts was assessed subjectively by a scaled estimate. The patients were required to assess a sample of 79 black-and-white and color contrasts according to a five-point scale comprising the ratings "much too low", "low", "optimal", "high", "much too high". The visual fields (outfield, infield) were either colorless or contained the colors yellow, green, red, purple or blue. The study involved 59 patients with age-related macular degeneration. Ninety percent of the patients were over 65 years old. There were twice as many women as men. The control group population consisted of 43 emmetropic subjects. In black or white infields on a colorless background (light gray to dark gray), a slight preference for positive (infield lighter than the background) contrast situations was found. The optimal contrasts were in the range of [K[ > 0.91. When colored infields were presented on a colorless background, the light infield colors yellow and green were preferred. The optimal contrast level was found to be [K[ > 0.85. Similarly, when colorless and colored infields were presented, light infield colors (white, yellow, green) on a dark background (purple, blue) were preferred. In selecting contrasts, subjects with impaired vision because of age-related macular degeneration preferred positive contrasts, i.e., mainly white, yellow and green on a colored or colorless background. These results provide information that can be used in designing orientation aids, e.g., road striping and lines, edges of stairs, handrails, timetables, etc. Conflicts of interest with emmetropic subjects is not to be expected. Subjects in the control group, while preferring similar contrasts, were ready to accept a wider range than the partially sighted.

Aged↗

PubMed2002

Near-field optical microscopy with video signal processor to apply a CCD imaging device as a variable area photo-sensor for improving operability and spectrum mode imaging.

We have developed a video signal processor for improving the operability and function of scanning near-field optical microscopy (SNOM). The video signal processor applies a CCD imaging device as a variable area photo-sensor in the SNOM unit instead of conventional photo-detectors. The signal processor converts the intensity of a selected area in video frames to a numerical value with a rate of 30 Hz. Consequently, the CCD imaging device can be used as a photo-detector of variable areas and positions for detecting a small area of a optical probe position. The need for a precise optical axis alignment is relaxed due to the large sensing area of the CCD device. Using the video signal processor, near-field optical and topographic images have been obtained by SNOM/AFM system simultaneously. By adding a spectrometer between the SNOM unit and the CCD device, the spectrum signal of selected wavelength ranges has been monitored by the video signal processor to provide an optical image.

Journal Article↗

PubMed2006

Development of a quasi-phase-matched, second-harmonic generation periodically poled lithium niobate waveguide with an integrated electro-optical modulator.

A novel type of waveguide quasi-phase-matched device with output electro-optical (EO) modulation is proposed and demonstrated. The second-harmonic generated output can be modulated with a high extinction ratio by integration of dual EO phase modulators on a periodically poled lithium niobate waveguide. Blue and green coherent light with EO modulation was demonstrated, and wavelength dispersion of r33 is discussed.

Journal Article↗

PubMed2005

Dual modulation of a molecular switch with exceptional chiroptical properties.

The ability to modulate the chiroptical properties of optically active molecules induced by external stimuli such as light, heat, and electrical fields allows for the design and development of molecular switches, memory devices, sensors, and photonic devices. A helical o-terphenyl compound functionalized with photoresponsive azobenzene and electroactive imide groups is designed as a dual-mode chiroptical molecular switch. Its exceptional optical activity (e.g., [alpha]436 = -9500) can be changed and modulated through photoisomerization of the azobenzene moiety using UV and visible light. Reversible modulation by electrochemical means was also achieved through the redox reaction occurring at the imide group. Large chiroptical read-out signals were observed during the redox cycles as indicated by the molar ellipticity values as high as 285,000 deg.cm2.dmol-1. Exceptionally high optical activity and large responses to both light and electrical bias make this chiral molecule suitable for the development of new molecular switches, sensors, and other optical devices.

Biphenyl Compounds↗

PubMed2006

Optical conformal mapping.

An invisibility device should guide light around an object as if nothing were there, regardless of where the light comes from. Ideal invisibility devices are impossible, owing to the wave nature of light. This study develops a general recipe for the design of media that create perfect invisibility within the accuracy of geometrical optics. The imperfections of invisibility can be made arbitrarily small to hide objects that are much larger than the wavelength. With the use of modern metamaterials, practical demonstrations of such devices may be possible. The method developed here can also be applied to escape detection by other electromagnetic waves or sound.

Journal Article↗