Optical Fiber Devices Research Articles

The peptide AF-16 decreases high interstitial fluid pressure in solid tumors

Background. The high interstitial fluid pressure (IFP) in solid tumors restricts the access to nutrients, oxygen and drugs. Material and methods. We investigated the ability of the peptide AF-16, involved in water and ion transfer through cell membranes, to lower the IFP in two different solid rat mammary tumors, one chemically induced, slowly growing, and the other transplantable, and rapidly progressing having high cellularity. AF-16 was administered either in the tumor capsule, intranasally or intravenously. The IFP was measured by a miniature fiber optic device. Results. AF-16 significantly lowered the IFP in both the slowly and the rapidly progressing tumors, whether administrated locally or systemically. The AF-16 induced IFP reduction was maximal after 90 min, lasted at least 3 h, and returned to pretreatment levels in less than 24 h. Topical AF-16 transiently reduced the IFP in the DMBA tumors from 17.7 ± 4.2 mmHg to 8.6 ± 2.1 mmHg. Conclusion. We conclude that AF-16 transiently and reversibly lowered the high IFP in solid tumors during a few hours, which might translate into improved therapeutic efficacy.

Zinc Selenide Optical Fibers

Semiconductor waveguide fabrication for photonics applications is usually performed in a planar geometry. However, over the past decade a new field of semiconductor-based optical fiber devices has emerged. The drawing of soft chalcogenide semiconductor glasses together with low melting point metals allows for meters-long distributed photoconductive detectors, for example.[1,2] Crystalline unary semiconductors (e.g., Si, Ge) have been chemically deposited at high pressure into silica capillaries,[3,4] allowing the optical and electronic properties of these materials to be exploited for applications such as all-fiber optoelectronics.[5-7] In contrast to planar rib and ridge waveguides with rectilinear cross sections that generally give rise to polarization dependence, the cylindrical fiber waveguides have the advantage of a circular, polarization-independent cross section. Furthermore, the fiber pores, and thus the wires deposited in them, are exceptionally smooth[8] with extremely uniform diameter over their entire length. The high-pressure chemical vapor deposition (HPCVD) technique is simple, low cost, and flexible so that it can be modified to fill a range of capillaries with differing core dimensions, while high production rates can be obtained by parallel fabrication of multiple fibers in a single deposition. It can also be extended to fill the large number of micro- and nanoscale pores in microstructured optical fibers (MOFs), providing additional geometrical design flexibility to enhance the potential application base of the fiber devices.[9] Semiconductor fibers fabricated via HPCVD in silica pores also retain the inherent characteristics of silica fibers, including their robustness and compatibility with existing optical fiber infrastructure, thus presenting considerable advantages over fibers based on multicomponent soft glasses.

Assessment of radiofrequency self‐heating around a metallic wire with MR T1‐based thermometry

Heat produced by a magnetic resonance (MR) imaging sequence in the vicinity of a conductive wire (pacemaker, electrodes, or catheter), is a subject of interest for the assessment of patient safety during imaging. For this purpose, the measurement of temperature rises during an MR imaging sequence using MR T1-based thermometry provides several advantages, mainly in its ability to retrieve in situ real-time thermal maps. Recent studies investigated the heat produced by an independent radiofrequency pulse, assessing MR imaging sequence heating using a specific MR thermometry sequence. This study focuses on self-heating for which the radiofrequency pulses used for measuring temperature create the heat. An experimental design was set up to evaluate T1-based thermometry self-heating using a coupled/decoupled wire and to compare it with a reference temperature gathered by an optical fiber device. For the tested experimental set up, T1-based thermometry is in fairly good agreement with optical fiber reference temperature.

Optical fiber sensing element based on luminescence quenching of silica nanowires modified with cryptophane-A for the detection of methane

An optical fiber sensing element based on luminescence quenching of cryptophane-A/silica nanowires was successfully constructed and used to dynamically monitor methane gas at low concentration below 3.5% (v/v). The optical fiber device was designed to operate via luminescence reflection. The sensing properties of optical sensing element to methane at room temperature were characterized. The sensing element shows an intensive and stable blue luminescence when excited by UV light source at wavelength of 380 nm, and it is efficiently quenched by molecular methane. The response of the sensing element demonstrates excellent linear Stern–Volmer behavior at the fixed wavelength 439 nm within the methane concentration range between 0.1% and 3.5% (v/v). A detection limit of below 0.1% (v/v) is estimated for the methane sensing element. This newly developed methane sensing element has significant advantages over the currently available methane sensors such as fast response and recovery (within seconds), good repeatability, selectivity, and long-term stability.

Experimental arrangement to measure dispersion in optical fiber devices

Dispersion is a quite important parameter in systems based on optical fiber, especially in pulsed emission lasers, where the temporal width is affected by such parameter. Therefore, it is necessary to consider the dispersion provoked by each component in the cavity. There are various experimental interferometric arrangements to evaluate this parameter. Generally, these systems modify the wavelength to obtain information about the n(λ) dependency, which is contained in the interferogram phase. However, this makes the system quite slow and it requires tunable and narrow bandwidth laser sources. In the present work, results obtained from an arrangement based on Mach-Zehnder interferometer where one of the arms is the optical fiber under study, while the reference one is air, are presented. In order to determine the n(λ) dependency, a wide spectrum light source was used in the wavelength range of interest. The phase information was evaluated from the interferometric signal measured by an optical spectrum analyzer.

Polarization Characteristics of the Deformed Low-Mode Fiber Waveguides with Polarization Conservation

In this work the results of polarization researches of low-optical fiber waveguides with conservation of polarization are presented. Obtained results quite convincingly testify regarding a high sensitivity low-mode regime of work of an optical fiber to anisotropic external influences, in comparison with one-mode regime of work of the same fibre. This result, can represent a big practical value at the realization of high-sensitivity fiber-optical devices of different physical values.

Non-invasive, MRI-compatible fibreoptic device for functional near-IR reflectometry of human brain

A non-invasive device for measuring blood oxygen variations in human brain is designed, implemented, and tested for MRI compatibility. The device is based on principles of near-IR reflectometry; power LEDs serve as sources of probing radiation delivered to patient skin surface through optical fibres. Numerical Monte Carlo simulations of probing radiation propagation in a multilayer brain model are performed to evaluate signal levels at different source — detector separations at three operation wavelengths and an additional wavelength of 915 nm. It is shown that the device can be applied for brain activity studies using power LEDs operating at 830 and 915 nm, while employment of wavelength of 660 nm requires an increased probing power. Employment of the wavelength of 592 nm in the current configuration is unreasonable.

A Novel Electrically Tunable Long-Period Fiber Grating Using a Liquid Crystal Cladding Layer

The main aim of the presented work is the integration of a long-period fiber grating and a liquid crystal into a hybrid structure, in order to develop an innovative fiber optic device controlled by an external electric field. The studied long-period fiber grating was fabricated using UV irradiation in a boron co-doped fiber (PS1250/ 1500, manufactured by Fibercore). As a liquid crystal we used a typical 5CB nematic liquid crystal. The sensing mechanism of the proposed loss filter relies on long-period fiber grating attenuation bands sensitivity to optical properties of the liquid crystal layer. The results obtained show that the long-period fiber grating with a nanosized liquid crystal layer exhibits one order of magnitude higher electrical sensitivity and a lower level of the voltage control than the long-period fiber grating with a micro-sized liquid crystal layer. PACS numbers: 42.81.Cn, 42.79.Dj, 42.81.Pa, 42.79.Kr

Coupled dielectric waveguides with photonic crystal properties

A system of planar waveguides coupled through a periodic set of small windows is considered. It is shown that the weak periodic coupling of the waveguides leads to an additional eigenvalue band separated by a gap from the threshold of a continuous spectrum branch. Thus, the system has photonic crystal properties, which can be used to construct optical fiber devices. This system can also play the role of a SCISSOR device for reducing the group velocity of light, in optical delay lines, etc.

Resonances in coated long period fiber gratings and cladding removed multimode optical fibers: a comparative study

Two optical fiber devices have been coated in parallel: a long period fiber grating (LPFG) and a cladding-removed multimode optical fiber (CRMOF). The progressive coating of the LPFG by means of the layer-by-layer electrostatic-self-assembly, permits to observe a resonance wavelength shift of the attenuation bands in the transmission spectrum. The cause of this wavelength shift is the reorganization of the cladding mode effective indices. The cause of this modal reorganization can be understood with the results observed in the CRMOF coated in parallel. A lossy-mode-resonance (LMR) is generated in the same wavelength range of the LPFG attenuation bands analyzed. Moreover, the thickness range where the wavelength shift of the LPFG attenuation bands occurs coincides exactly with the thickness range where the LMR can be visualized in the transmission spectrum. These phenomena are analyzed theoretically and corroborated experimentally. The advantages and disadvantages of both optical fiber devices are explained.

ChemInform Abstract: Solid-State Sensors for Trace Hydrogen Gas Detection

This paper reviews the development, history, theoretical basis, and experimental performance of solid‐state hydrogen detectors under flow‐through conditions available to date such as pyroelectric, piezoelectric, fiber optic, and electrochemical devices. Semiconductor hydrogen detectors will only be reviewed briefly, as excellent reviews on this subject already exist. In view of the fact that almost all the devices that will be discussed later in this paper use Pd as a hydrogen trap, we devote a subsection to examining the role of palladium as a catalyst as well as some of the characteristics of the Pd‐H2 system. Non‐solid‐state hydrogen sensors, such as the flame ionization detector are not the object of this review. A useful feature of this review is a comparison of operating characteristics of each device in a general table in Sec. VII. In that section a general discussion is presented, including a critical comparison of the capabilities and parameters of various solid‐state hydrogen sensors in the form of a table showing data collected from the literature. The Pd‐fiber optic sensor is the most sensitive optical device operating at room temperature. The Pd‐photopyroelectric sensor appears to be most economical and second best in sensitivity at room temperature; it has the best potential for high signal‐to‐noise operation at the widest temperature range, down to cryogenic temperatures. The Pd‐field effect transistor devices exhibit the second highest sensitivity at elevated temperatures.

Microfluidic biolector—microfluidic bioprocess control in microtiter plates

In industrial-scale biotechnological processes, the active control of the pH-value combined with the controlled feeding of substrate solutions (fed-batch) is the standard strategy to cultivate both prokaryotic and eukaryotic cells. On the contrary, for small-scale cultivations, much simpler batch experiments with no process control are performed. This lack of process control often hinders researchers to scale-up and scale-down fermentation experiments, because the microbial metabolism and thereby the growth and production kinetics drastically changes depending on the cultivation strategy applied. While small-scale batches are typically performed highly parallel and in high throughput, large-scale cultivations demand sophisticated equipment for process control which is in most cases costly and difficult to handle. Currently, there is no technical system on the market that realizes simple process control in high throughput. The novel concept of a microfermentation system described in this work combines a fiber-optic online-monitoring device for microtiter plates (MTPs)--the BioLector technology--together with microfluidic control of cultivation processes in volumes below 1 mL. In the microfluidic chip, a micropump is integrated to realize distinct substrate flow rates during fed-batch cultivation in microscale. Hence, a cultivation system with several distinct advantages could be established: (1) high information output on a microscale; (2) many experiments can be performed in parallel and be automated using MTPs; (3) this system is user-friendly and can easily be transferred to a disposable single-use system. This article elucidates this new concept and illustrates applications in fermentations of Escherichia coli under pH-controlled and fed-batch conditions in shaken MTPs.

Performance improvement of optical fiber coupler with electric heating versus gas heating

Gas heating has been widely used in the process of fused biconical tapering. However, as the instability and asymmetric flame temperature of gas heating exist, the performance of the optical devices fabricated by this method was affected. To overcome the problems resulting from gas combustion, an electric heater is designed and manufactured using a metal-ceramic (MoSi(2)) as a heating material. Our experimental data show that the fused-taper machine with an electric heater has improved the performance of optical devices by increasing the consistency of the extinction ratio, excess loss, and the splitting ratio over that of the previous gas heating mode. Microcrystallizations and microcracks were observed at the fused region of the polarization-maintaining (PM) fiber coupler and at the taper region with scanning electron microscopy and atomic force microscopy respectively. The distribution of the microcrystallizations and microcracks are nonuniform along the fiber with gas heating, while their distribution is rather uniform with electric heating. These findings show that the novel optical fiber coupler with an electric heater has improved the performance of optical fiber devices by affecting the consistency of the optical parameters and micromorphology of the surface of PM fiber.

Judd–Ofelt analysis and improvement of thermal and optical properties of tellurite glasses by adding P2O5

Abstract Er3+ and Er3+/Yb3+ co-doped tellurite glasses, suitable for developing optical fiber laser and amplifier, have been elaborated from the conventional melt-quenching method. Results of differential scanning calorimetry (DSC) measurements indicate a good thermal stability of tellurite glasses. The DSC measurements show an improvement of thermal stability of glass hosts after adding P2O5. Absorption spectrum from near infrared to visible was obtained and the Judd–Ofelt (J–O) intensity parameters (Ω2, Ω4, and Ω6) were determined. Spontaneous emission probabilities of some relevant transitions, branching ratio, and radiative lifetimes of several excited states of Er3+ have been predicted using intensity J–O parameters. Absorption cross-section and calculated emission cross-section, using the McCumber method, for the 4I13/2→4I15/2 transition, were determined and compared for the doped and co-doped glasses. Energy transfer (ET) and effect of changing concentration of P2O5 and Yb3+ ions on spectroscopic properties were investigated. It was found that the addition of P2O5 can increase the symmetry of the Er3+ ion. As a consequence, PL lifetime becomes more longer. The spectroscopic properties and the efficient infrared luminescence indicate that Er3+ doped TeO2–ZnO–Na2O–Er2O3 (TZNE) is a promising laser and amplifier materials and may be a potentially useful material for developing upconversion fiber optical devices.

Bragg Gratings Written in Tapered Solid-Core Photonic Crystal Fibers

Fiber Bragg gratings are very useful in many applications. This is why a higher control of their properties is desirable. Therefore, a grating preprocessing technique, based on the dependence of the index guided photonic crystal fiber (IG-PCF) properties on their structural parameters, is proposed allowing a higher control of the Bragg wavelength. Using the proper combination of thermo-mechanical IG-PCFs tapering and ultraviolet photoinscription methods, it is possible to develop new optical fiber devices. Their effectiveness is demonstrated by comparison with the results on single-mode fiber. Finally, to demonstrate the feasibility of the technique, a wideband chirped Bragg grating is fabricated.

Fiber‐optic Singlet Oxygen [1O2 (1Δg)] Generator Device Serving as a Point Selective Sterilizer

Traditionally, Type II heterogeneous photo-oxidations produce singlet oxygen via external irradiation of a sensitizer and external supply of ground-state oxygen. A potential improvement is reported here. A hollow-core fiber-optic device was developed with an "internal" supply of light and flowing oxygen, and a porous photosensitizer-end capped configuration. Singlet oxygen was delivered through the fiber tip. The singlet oxygen steady-state concentration in the immediate vicinity of the probe tip was ca 20 fm by N-benzoyl-DL-methionine trapping. The device is portable and the singlet oxygen-generating tip is maneuverable, which opened the door to simple disinfectant studies. Complete Escherichia coli inactivation was observed in 2 h when the singlet oxygen sensitizing probe tip was immersed in 0.1 mL aqueous samples of 0.1-4.4 x 10(7) cells. Photobleaching of the probe tip occurred after ca 12 h of use, requiring baking and sensitizer reloading steps for reuse.

Hardwood-Nuss’ Clinical Practice of Emergency Medicine, Fifth Edition

Hardwood-Nuss’ Clinical Practice of Emergency Medicine, Fifth Edition

Effect of pedal pump and thoracic pump techniques on intracranial pressure in patients with traumatic brain injuries.

Although osteopathic manipulative treatment (OMT) is used to manage myriad conditions, there has been some hesitation regarding the safety of applying OMT to patients with intracranial injuries or elevated intracranial pressure (ICP). To assess the safety of two OMT techniques--pedal pump and thoracic pump--on ICP and cerebral perfusion pressure (CPP) in patients with traumatic brain injuries (Glasgow Coma Scale score < or =8). We prospectively enrolled consecutive patients admitted to the intensive care unit (ICU) for traumatic brain injury. Patients between the ages of 18 and 75 years and with abnormal CT scans were included in the present study. Patients with baseline ICP values of 20 mm Hg or lower were assigned to group 1, and those with ICP levels greater than 20 mm Hg, group 2. Patients underwent continuous ICP and CPP monitoring, with ICP measured using a ventricular catheter and fiber optic device. Values of ICP and CPP were recorded at baseline, during application of the OMT techniques, and 5 minutes after the two OMT techniques were completed. Patients received up to three treatment cycles. Ventricular drains remained open (stopcock open) during OMT, allowing continued cerebral spinal fluid drainage, except for brief periodic closures (stopcock closed) every minute to register accurate ICP values. Statistical analysis was performed using a dependent t test with repeated measures. Twenty-four comatose patients, aged 18 to 69 years, received a total of 50 sessions of pedal pump and thoracic pump techniques. In group 1 patients, a slight decrease in ICP values (mean, -0.586 mm Hg) and an increase in CPP values (mean, 1.1613 mm Hg) was noted post-OMT. Patients in group 2 also had decreased mean ICP values (-1.20 mm Hg) and increased mean CPP values (2.2105 mm Hg). Changes were not statistically significant in either group. According to the present limited study, pedal pump and thoracic pump techniques may be used safely in patients with severe brain injuries.

Analysis of liquid crystals orientation in microcapillaries

Growing interest in photonic liquid crystal fibers, as relatively easily controllable optical fiber devices, force us to examine the quality of orientation of liquid crystals infiltrating a photonic crystal fiber. In this letter, we present a novel method of orientation analysis of liquid crystals in microcapillaries. Full Text: PDF

Emergency airway management using the Bonfils intubation fiberscope

The difficult airway is a challenge to both the emergency physician and the anesthesiologist. Its incidence in the Emergency Department (ED) is understandably higher as there is a disproportionately larger number of patients requiring airway management as a result of acute medical or surgical conditions, which by themselves contribute to the difficulty and because the patients are not prepared for intubation as during elective surgery [1]. Many videobased intubation devices have been developed as an alternative to flexible fiberoptic bronchoscope intubation and direct laryngoscopy for difficult airway management and various rigid fiberoptic stylets have been proposed [2], including the Bonfils retromolar intubation fiberscope, a recently re-discovered airway device designed in the 1980s (Karl Storz Co., GmbH, Tuttlingen, Germany) (Fig. 1, 2). It is a reusable, rigid, straight fiberoptic device with a 40 curved tip, 40 cm long and 5 mm in diameter. A flexible eyepiece is mounted on the handle of the scope. The fiberscope has a connector that fits onto the 15-mm tracheal tube adapter and thereby allows oxygen insufflation. A cold light source or a small battery handle can be attached to the stylet handle. The tip of the Bonfils intubation fiberscope is positioned just proximal to the tip of the attached endotracheal tube, thereby preventing the lens from being soiled with blood or secretions, and to reduce any risk of mucosal trauma. We report on ten patients in whom the Bonfils intubation fiberscope was used for emergency endotracheal intubation in an Emergency Department (ED). All described cases were performed by a specialist in Anesthesia and Intensive Care Medicine, experienced in airway management procedures. The following is a paradigmatic case: a 52-year-old man was admitted to the ED with blunt thoraco-abdominal trauma, with multiple open fractures. Potential cervical spine injury was assumed by the first responders, and treated with a rigid cervical immobilization collar. The primary survey, revealed obesity (BMI: 38). The blood pressure was 70/50 mmHg, pulse rate 112 beats/min, respiratory rate 40 breaths/min, and the oxygen saturation 89% on a non-rebreathing face mask (FiO2: 1). He was alert but confused (GCS 11): the patient needed a definitive airway. He had several predictors of difficult intubation: obesity, limited neck mobility, limited mouth opening (mouth opening less than three finger breadths). The patient was supine on a long spine board. Preoxygenation was performed with 100% O2 for at least 3 min by a tight seal facemask. Bag mask ventilation (BMV) was not considered difficult, and rapid sequence intubation was performed with intravenous midazolam 5 mg, ketamine 100 mg, and succinylcholine (100 mg). The Bonfils fiberscope, armed with an 8-mm inner diameter standard endotracheal tube, was inserted with the right retromolar approach to avoid cervical movements, with a jaw thrust maneuver performed with the left hand to increase the size of the retropharyngeal space. Advancing the Bonfils into the glottic aperture, the TT was gently and successfully inserted by a counterclockwise anterior rotation under direct vision of the trachea. Tube position was further checked with chest auscultation and capnography, and the intubation time was less than 1 min. In addition to the case described above in detail, the Bonfils intubation fiberscope was electively used in nine R. M. Corso (&) G. Gambale E. Piraccini Emergency Department, Anaesthesia and Intensive Care Unit, Ospedale ‘‘G.B. Morgagni-Pierantoni’’ Viale Forlanini, 34, 47100 Forli, Italy e-mail: rmcorso@gmail.com