Window Seal Research Articles

Optical imaging combined with targeted electrical recordings, microstimulation, or tracer injections

To facilitate the combination of optical imaging with various electrode-based techniques, we have designed and produced a skull-mounting ‘sliding-top cranial window’ and a removable ‘electrode positioner microdrive’. These new devices were used to study sensory processing in chronic and acute experiments in the cerebral cortices of cats and monkeys. This assembly allows simultaneous optical imaging of intrinsic signals or voltage-sensitive dyes combined with extracellular recording (single and multiple unit recording and local field potential), intracellular recording, microstimulation, or targeted injection of tracers. After the functional architecture is determined by optical imaging, electrodes are targeted into a selected cortical site under full visual control, at a variety of penetration angles (30–90°), accessing a large cortical area. The device consists of three parts: (1) a skull-mounting chamber, (2) a sliding cap, and (3) a microdrive. The microdrive can easily be removed and the cranial window is then sealed and covered with a flat protective cover. For chronic experiments, this arrangement allows the animal to be handled over a long period while fitted with a sealed cranial window of minimal volume and weight, and with negligible risk of accidental damage or infection.

Elastomer for window seals

Elastomer for window seals

Weatherability of coated EPDM rubber compound by controlled UV irradiation

Polymeric composites for automotive window seal applications are generally exposed to complex service environment conditions. The fundamental physico-chemical processes that control the durability of such composite systems on a micro and macroscopic level were evaluated in the present case using thermal analysis (TA), elemental mapping and microscopy. Five different EPDM rubber compounds (control, three bulk modified and one surface modified), coated with polyurethane coating were exposed to controlled UV irradiation. The higher the adhesion, the less the extent of UV penetration through the interface. The photo-oxidation mainly takes place from the surface, as the energy gets consumed and the intensity of the UV decreases on its passage through the strongly adhered layers to the rubber compound. The coating layer being on the surface, is more affected and photodegraded by UV irradiation than the rubber compound. The sample P 1cc, being multiphasic in nature and with a strong interface, can scatter the UV strongly and hence shows best weatherability among all the systems.

A sealed cranial window system for simultaneous recording of blood flow, and electrical and optical signals in the rat barrel cortex

We have developed a new sealed cranial window technique which allows the manipulation of simultaneously and independently multiple sensor probes, such as a glass microelectrode and a laser-Doppler probe. possible. Furthermore, normal intracranial pressure (4 mmHg) can be maintained throughout the craniectomy and the experiment. Using this technique, we have measured the neuronal activity and local cerebral blood flow together with the intrinsic optical properties in the rat barrel cortex during mechanical stimulation of the whiskers. The onset of the field response recorded by an extracellular electrode in the principal barrel columns occurred about 8 ms from the beginning of stimulation. These responses were well correlated with the whisker displacements (3 Hz, 2 s). The local cerebral blood flow, measured by laser-Doppler flowmetry, started to increase about 0.5 s after the first field response, peaked at about 1.7 s, and then gradually waned. A similar time-course of changes in the local blood volume was observed by simultaneous intrinsic optical imaging at the hemoglobin-isosbestic wavelength (570 nm). These results suggest that our technique would be useful for assessing the mechanism underlying neurovascular coupling under physiological conditions in vivo.

Hydrostatic optical cell for temperatures below 350 K and pressures to 400 MPa

A compact optical pressure cell tested at pressures up to 400 MPa is presented. The cell has been used within the temperature range 10–350 K. The cell has a small mass of 0.2 kg which facilitates rapid changes in temperature. A new high-pressure window seal is presented which allows the cell to be mounted directly in vacuum with no leak over its entire temperature and pressure range. A method of attaching the cell to common coldhead-type cryostats and closed-cycle refrigerators is presented.

Environmental control of indoor biologic agents

Environmental control of indoor biologic agents

Environmental control of indoor biologic agents

The indoor environment contains unique pollutants, such as environmental tobacco smoke and indoor allergens. In addition, air pollutants may reach higher levels indoors than outdoors, and in some instances may exceed the national standards for outdoor exposure. Nonindustrial indoor settings, such as offices, residences, and vehicles, also have air quality problems. Although the role of occupational air pollutants (organic and inorganic) in causing complaints in the workplace has been clearly documented, the relationship between poor air quality and health complaints is often controversial. The main causes of poor indoor air quality are an inadequate ventilation or fresh air intake, biologic contamination of the indoor environment, and an accumulation of noxious compounds. A list of important indoor air pollutants is shown in Table I. Because indoor allergen concentrations are higher in homes than in public places, a greater effort should be made to control allergens at home. A reason for this difference may be the more aggressive chemical treatment of carpets in public places. However, in some instances high mite, cat, and dog allergen levels have been detected in schools and day care centers. These findings have important implications for families who are practicing allergen avoidance at home because the effort and time spent controlling allergen exposure could be jeopardized by exposure in the school environment.' Studies conducted in schools have demonstrated that carpets contain high levels of a variety of allergens including pollen, cat, dog, food, mite, and mold allergens.2 Carpets in schools and homes are an important reservoir of allergens.

A wide wavelength range spectrometer (1150–8000 Å) for the RFX reversed field pinch experiment

This paper describes the vacuum Czerny–Turner spectrometer with a 1.33 m focal length installed on the RFX fusion experiment. The optics are coated with MgF2 and the image intensifier, protected by a vacuum sealed MgF2 window, features a dual photocathode system, CsTe on one half and S20 on the other; thus the instrument covers efficiently the wide spectral range from the MgF2 limit to the near infrared. Sensitivity at short wavelengths is limited by the reflectance of mirrors and the transmittance of the MgF2 window. The detector is completed by a fast optical multichannel analyzer whose 1024 photodiodes can be read out in a time of 250 μs. The instrument can also be operated in a duochromator mode by deflecting the diffracted beam onto a second detector system, where two photomultipliers are applied to two exit slits, one fixed and the other remotely movable in such a way that the intensity ratios of two lines can be monitored for diagnostic purposes. Some examples of obtained spectra illustrating the instrument performance and comprising first results from the RFX plasma are presented.

Radiant heater assembly for limited reaction-rate processing applications

We discuss the design and performance of a radiant heating assembly for limited reaction-rate processing applications. The heating assembly is fabricated in stainless steel on a 300 mm bore flange for incorporation with an ultrahigh vacuum compatible low-pressure chemical vapor deposition system. The heating source is an array of 18 tungsten-halogen lamps; each lamp is rated at 360 W and has its own integral parabolic reflector. A 55-mm-diam ‘‘O’’ ring sealed quartz window is mounted in front of each lamp allowing the transmission of infrared radiation into a water-cooled stainless-steel deposition chamber.

Improving My Average

IMPROVING MY AVERAGE / Kate Wheeler THE PROP PLANE LABORED up the Andes' blue and white spine, at the mercy of blasts and vacuums. My scrambled eggs jittered in their dish, like the coarse yellow foam that storms leave on a beach. I had no intention of eating them: I was counting cities on my fingers, dividing in my head. After calculating backwards twice, I'd just gotten it straight. Being twelve years old, having lived in eight places, I'd inhabited each location of my childhood for one and four-eighths years, eighteen months, too long. When I'd arrived where we were now leaving, I was seven and had lived in seven places. I'd been in a state of perfect balance, I now realized, like the Golden Age of Pericles: I couldn't remember having worried about anything. But then my dad's company kept him five years in Terremotos, Perú. In the yellow desert of the north, I grew old enough for first loves—skinny Mike Grady, who could walk on his knees in lotus pose, and the Pacific Ocean, which almost claimed me one day in an undertow. Time stretched out so long in Terremotos, I forgot it was dragging me toward this, the day of departure. Now we were moving to Cartagena, Colombia, on the bathtubshallow Caribbean. My father's company had promoted him to manage a plant that extruded polyethylene. I'd be able to see Plásticos Revo across the bay from my own balcony, promised my mother, who'd made a househunting trip a month ago and rented the same house my father's predecessor had lived in. "I hope we leave it soon," I said meanly when she showed me the picture of the house, pink and modern, with a rubber tree over the garage. "You jackal, I worked so hard," she said, and burst into tears. "Eat those eggs," she told me now. "A protein breakfast is the best gift you can give your brain." Before I could hesitate, my father's eye rolled over onto me, and I heard him clear his throat. "Lila." I stabbed them, wishing I could throw them out the sealed window for condors to eat. The plane's silver wing hung over the Cordillera Blanca, perfectly static, as if we weren't really moving. If we crashed, Td touch snow for the first time. I imagined search parties of cholos fanning The Missouri Review · 142 out over a glacier, chewing coca leaves for endurance. By the time they found us, most of the passengers would be frozen, dreaming their way deeper and deeper into total darkness. Not me—I'd read in Jack London how to bury yourself in a drift and remain alive, insulated by snow itself. Incas' descendants would adopt me; I'd live the rest of my life on the altiplano, playing a quena among stone ruins. We landed, and Cartagena clapped itself around us like a boiled towel. The Customs official smirked as he ran his hands under my mother's nighties, examined the soles of my U.S.—made saddle shoes for marks of use. He envied us, I knew. Still, I wanted to explain that I'd been born in the jungle in Venezuela, and so wasn't blood-connected with this mortifying mountain of imported goods. Because our main shipment wasn't due for several months, my mother had packed everything from aspirin to bedspreads in fifteen suitcases. My father's new driver took charge of us outside Customs. His name was Cosme Leña. He was the color of a plum and had no voice, only a kind of hiccup like the catch between sobs. As he gesticulated at the porters, my mother explained that Cosme had had a tracheotomy, and so lacked vocal cords. The operation was performed on the HOPE ship, a fact Cosme was proud of, my mom said, with a minuscule lifting of her eyebrows. I saw the scar in the pit of his throat, darker-purple, thickened skin, like a splash of glaze on ceramic. Mom and I squeezed in back with five suitcases. Cosme babied the company Fairlane along ruts...

Improved indium seal for LiF windows of resonance lamps for use at low temperatures

A method of attaching crystalline LiF windows to glass lamps has been developed. The resulting seals have good vacuum properties and can be cooled to cryogenic temperatures while maintaining their vacuum integrity. The technique uses dual, indium O rings to provide a vacuum seal for a LiF window on a resonance lamp. It is appropriate for resonance lamps that produce line spectra. LiF crystals must be cooled to transmit Lyman-β radiation that can optically pump atomic hydrogen. This indium seal has other applications such as windows for VUV lasers. Details of the construction, assembly, and performance of the seal are described. A discussion of the merits and applications of the window seal is presented.

High-temperature window seals for VUV experiments

A simple and reliable technique for sealing laser quality vacuum-ultraviolet grade windows to high-temperature, bakable vacuum systems has been developed. Both 7.5-cm-diam MgF2 and CaF2 windows were found to be He leak tight to temperatures exceeding 330 °C. Smaller 4-cm-diam windows seal at temperatures exceeding 400 °C. The seals do not appear to be adversely affected by temperature cycling and they do not distort the optical quality of the window. The sealing technique has been used without failures in a Hg vapor four-wave-mixing cell that is used to produce high-power 130-nm coherent radiation.

Thirty years of stapes surgery.

The modern stapedectomy with prosthesis insertion and living oval window seal, like the modern cataract extraction with lens replacement, is now performed, very much the same, throughout the world. I have reviewed the evolution of stapes surgery during these last thirty years and tried to gain some agreement for several important facts about otosclerosis and several basic principals of stapes surgery. While a well-performed stapedectomy can eliminate the conductive component, the sensorineural hearing loss continues and, in about one-third, will progress till the patient, after age 65, must return to a hearing aid. A piston prosthesis gives the best hearing results: 0.6 mm diameter, when half the footplate is removed and a living oval window seal interposed, and 0.6 mm diameter when a small opening is made in the footplate obliterated by otosclerosis. I prefer a teflon prosthesis to stainless steel because it can be altered by the surgeon at operation, and vein as an oval window seal. I have presented a rare group of patients who develop facial palsy 5-1/2 days after uncomplicated stapedectomy, of whom all recover quickly and completely. I am confident that progress will continue to be made in the understanding of otosclerosis, and the performance of stapes surgery, but in these last thirty years we have made a good beginning.

Middle Ear Infection Postimplantation: Response of the round Window Membrane to Streptococcus Pyogenes

The seal of the implanted round window membrane to resist Streptococcus pyogenes invasion from the middle ear was investigated in 12 cats. Results showed that the implanted round window membrane is able to form a barrier for S pyogenes starting 1 week postimplantation. Under normal conditions S pyogenes did not pass through the round window membrane, nor through the gap that existed between the membrane and the prosthesis. Mechanical disruption of the round window seal, however, and severe inflammatory response to S pyogenes caused the infection to extend into the inner ear.

Indium seals for low-temperature and moderate-pressure applications

Some ideas as to what the important factors are that will produce a reliable indium O-ring seal are discussed. Four novel indium seal designs which are based on these ideas are presented. Three of these seals have been incorporated in a Brillouin cell. They include a simple sapphire window seal, a filling line union, and a flange seal. All of them have withstood low temperatures down to 77 K and moderate pressures up to 177 bar. The fourth seal described is a Pyrex tube seal for a Raman cell.

Tianjin photographic zenith tube observations

In this paper we analyse the observational data obtained by the Chinese-made PZT in the two periods 1979 Feb – 1980 May and 1981 Dec – 1983 March. The internal accuracy of single star is found to be m u = ±13.0 ms, m φ = ±0. “144 for the first period, and m u = ±14.6 ms, m φ = ±0.” 152 for the second. Correction of star position is found by the chain method. The systematic error caused by the sealed window of the evacuated chamber and the temperature effect of the plate scale are investigated. Monthly means of time and latitude are given.

Improved Proportional Counters for Practical Applications

Gas filled proportional counters are useful room-temperature X-ray detectors in various gauges and spectrometers. New gas mixtures have made it possible to improve the properties of these detectors. Penning mixtures offer some special advantages. These mixtures are formed when parent gas is diluted with a small amount of impurity whose ionization energy is lower than the lowest excited state of the parent atoms. The excitations of these atoms can subsequently be turned into ionizations. The result of this additional ionization is that the average ionization energy of the mixture falls below that of the pure gases. This also improves the energy resolution of the detector. Another feature of Penning mixtures is the fact that the first Townsend ionization coefficient is high. This in turn is reflected by an unusually low anode voltage required by the detector. This makes it possible to use high filling pressures and to realize the advantages such pressures offer: the achievement of good energy resolution with a commercial low noise preamplifier; a decrease in the background caused by the wall effect because of the subsequently shorter photoelectron traces; and an increase in the efficiency of the detector. The type of detector used in this paper ismore » a sealed side window counter. Some of its properties, when filled with the mixtures Ar-C/sub 4/H/sub 10/, Ar-Xe, and Ne-Ar, are presented.« less

Cochlear Implant Round Window Sealing Procedures in the Cat:An Investigation of Autograft and Heterograft Materials

In this series of experiments it was shown that a round window seal produced with a muscle autograft or a Teflon felt disc glued to the electrode, prevented a Staphylococcus aureus infection in the bulla extending to the cochlea. The seal following a fascial autograft also prevented β-haemolytic streptococci type A spreading to the basal turn of the cochlea. On the other hand, Dacron™ velour is contra-indicated as it was associated with a strong inflammatory response and a high incidence of infection. The studies also indicated that infection can extend to the cochlea before the round window membrane has healed. The junctional area between the graft and the margin of the round window niche, is a potentially vulnerable site.

Small fenestra stapedectomy technique: reducing risk and improving hearing.

During the past 25 years many variations have emerged in stapedectomy, most of which centered around either a change in the prosthesis itself or in the type of oval window seal. The small fenestra stapedectomy technique (SFT) represents a change in surgical procedure rather than in prosthetic design. This technique offers the opportunity to improve hearing results while reducing risks in stapedectomy surgery. Four areas of significant improvement are seen in patients in whom the SFT was used: (1) improved hearing in the high frequencies of 2000, 4000, and 8000 Hz, (2) improved speech discrimination scores, (3) a significant reduction in the number of reported vestibular complaints, and (4) a reduction in the number of serious postoperative sensorineural hearing losses.

Aluminium alloy-sapphire sealed window for ultrahigh vacuum

The first Potassium Diode Pumped Alkali Laser (DPAL) with flowing gain medium in closed cycle system has been demonstrated. A slope efficiency of 31% for continuous wave operation was achieved with a maximum output power 5 W. The flow loop was operated with a helium buffer gas pressure of 800 Torr and an alkali metal temperature of 185 °C. An examination of laser performance vs flow speed demonstrated higher efficiencies with increasing flow speeds.