Fiber Optic Spectrometer Research Articles

An Improved Method for Accurate Radiation Measurement Based on Dark Output Noise Drift Compensation.

This paper verified through experiments that change in ambient temperature are the main cause of dark output noise drift. Additionally, the impact of dark output noise drift in fiber optic spectrometers on emissivity measurements has been investigated in this work. Based on an improved fiber optic spectrometer, two methods were proposed for characterizing and correcting the dark output noise offset in fiber optic spectrometers: the mean correction scheme and the linear fitting correction scheme. Compared to the mean correction scheme, the linear fitting correction scheme is more effective in solving the problem of dark output noise drift. When the wavelength is greater than 1600 nm, the calibration relative error of silicon carbide (SIC) emissivity is less than 0.8% by the mean correction scheme, while the calibration relative error of silicon carbide emissivity is less than 0.62% by the linear fitting correction scheme. This work solves the problem of dark output noise drift in prolonged measurement based on fiber optic spectrometers, improving the accuracy and reliability of emissivity and quantitative radiation measurement.

In situ growth of AuNPs with a nanocavity on the surface of optical fibre for development of SPR sensor

Gold nanoparticles (AuNPs) integrated within optical fibres show great potential as sensor materials in the field of sensing, utilizing the Surface Plasmon Resonance (SPR) principle. This study presents a straightforward, cost-effective, and replicable approach for producing permanent in-situ embedding of AuNPs with nanocavities on the surface of optical fibres. The process involves chemical vapour etching (CVE), followed by gold sputtering and isothermal heat treatment. The analysis conducted using High-Resolution Transmission Electron Microscopy (HRTEM) and Energy-Dispersive X-ray Spectroscopy (EDX), confirmed the presence of nearly spherical AuNPs embedded on the surface of the optical fibre, with an average diameter of 60 ± 5 nm. Additionally, the detection of two distinct plasmon absorption peaks at 567 ± 5 nm and 620 ± 5 nm using a Fibre Optic Spectrometer further validated the presence of AuNPs. To verify the existence of nanocavities surrounding the AuNPs, Field Emission Transmission Microscopy (FESEM) was employed, along with subjecting the AuNPs embedded fibre to three different NaCl solutions of varying concentrations. The results supported the presence of a nanocavity encapsulating the AuNPs. A proposed mechanism was put forth to explain the spectral behaviour resulting from the creation of the nanocavity. This specialty optical fibre is expected to have broad applications in the development of SPR-based chemicals and biosensors, as it facilitates close interaction between the AuNPs and analytes through the nanocavity surrounding the AuNPs on the fibre surface. The fabrication process demonstrated excellent repeatability, with strong adhesion of AuNPs to the optical fibre surface, and no leaching even after repeated use. Thus, we believe that this fabrication method is an exceptional technique for permanently incorporating AuNPs into various glass-based optical waveguide materials for SPR-based sensing applications.

Ultra-Short Fiber Bragg Grating Used for Spectral Analysis of Guided Light in Single-Mode Fibers

An ultra-short fiber Bragg grating with a grating length of 0.2 mm and constant grating period (uniform FBG) is proposed as an integrated dispersive element for spectral analysis in a single-mode glass fiber. This dispersive element is used to set up a fiber optical spectrometer that demonstrated an average spectral resolving power of 825, a pixel resolution of 0.02 nm/pixel, and a 40 nm bandwidth covering the 810-850 nm wavelength range. Furthermore, the dependence of this dispersive element on light polarization was examined, which induces a reduction in the wavelength accuracy up to ±0.05 nm. Finally, the investigated spectrometer to function well as a part of a readout device for fiber Bragg grating sensors is presented. Short uniform Bragg gratings as dispersive elements allow the manufacturing of miniaturized, compact spectrometers without additional focusing components between the FBG and detector.

A Fiber-Optic Array Spectrometer With Parallel Multichannel Optical Lock-in Detection and its Application to in Situ Lighting Measurements

This paper describes a new optical spectroscopy instrument achieving lock-in detection in all its spectral output channels in a parallel and simultaneous fashion. It is based on two identical compact array spectrometers working in phase quadrature thanks to optical modulators synchronized with an external reference signal. <p xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">In the application example, the optical lock-in spectrometer was used to perform spectral irradiance measurements with commercial LED lamps exhibiting temporal light modulation at different frequencies. A remote sensing optical device was designed to measure from a distance the temporal luminous waveform of a specific LED lamp and send it to the reference input of the optical lock-in spectrometer. When the lamps were operating together on top of a large continuous luminous background, the optical lock-in spectrometer successfully retrieved the respective spectral irradiance distributions and color parameters of each lamp, allowing their characterization to be performed independently of the other light sources illuminating the sensor during the measurements.

Effect of the primary oxidizer stream jet velocities on the ignition and combustion characteristics of pulverized coal under MILD oxy-coal combustion conditions

MILD oxy-coal combustion technology is a prospective technology with the potential for CO2 capture and storage, and it is characterized by the intense flue gas recirculation to preheat the fuel and to dilute the oxidizer due to the oxidizer or fuel jet with high velocity. The effect of the primary oxidizer stream jet velocities ranging from 1.7 m/s to 11.2 m/s on the coal ignition and combustion characteristics were experimentally investigated on a flat flame pulverized coal burner at various oxygen concentrations of 5%-21% and gas temperatures of 1473–1873 K under O2/CO2 and O2/N2 atmospheres. The coal flame images were recorded by the digital camera, and the flame structure evolution and ignition delay times of coal particles were analyzed at different primary oxidizer stream jet velocities and hot coflow conditions. The coal combustion radiation spectrum was monitored by an optical fiber spectrometer and the coal particle temperatures were derived with the two-color pyrometry. The results showed that the bright yellow soot flame gradually disappeared with the decrease of O2 concentration when CO2 replaced N2. The difference of ignition delay times between O2/CO2 atmosphere and O2/N2 atmosphere decreased from 2.8 ms to 0.2 ms when the primary air jet velocity increased from 1.7 m/s to 11.2 m/s at 1473 K and 5% O2. This meant the elevated jet velocity was beneficial to offset the delayed effect of the physicochemical properties of CO2 on coal ignition. The peak coal particle temperature increased by 68 K at 1873 K and 5% O2 under O2/CO2 atmosphere with the highest jet velocity owing to the accelerated diffusion of O2 into coal particle stream. Moreover, a dimensionless coal particle temperature parameter η was proposed to characterize the variation of the peak coal particle temperature caused by the improved heat transfer and mass transport between the coflow and coal particles under high jet velocity. The maximum value of η was 1.053 at 1873 K and 21% O2 under O2/CO2 atmosphere with the jet velocity of 11.2 m/s, indicating the increased jet velocity had the predominant effect on the increase of peak particle temperature at high gas temperature and O2 concentration.

Transmissive Mode Laser Micro-Ablation Performance of Ammonium Dinitramide-Based Liquid Propellant for Laser Micro-Thruster.

The transmissive mode laser micro-ablation performance of near-infrared (NIR) dye-optimized ammonium dinitramide (ADN)-based liquid propellant was investigated in laser plasma propulsion using a pulse YAG laser with 5 ns pulse width and 1064 nm wavelength. Miniature fiber optic near-infrared spectrometer, differential scanning calorimeter (DSC) and high-speed camera were used to study laser energy deposition, thermal analysis of ADN-based liquid propellants and the flow field evolution process, respectively. Experimental results indicate that two important factors, laser energy deposition efficiency and heat release from energetic liquid propellants, obviously affect the ablation performance. The results showed that the best ablation effect of 0.4 mL ADN solution dissolved in 0.6 mL dye solution (40%-AAD) liquid propellant was obtained with the ADN liquid propellant content increasing in the combustion chamber. Furthermore, adding 2% ammonium perchlorate (AP) solid powder gave rise to variations in the ablation volume and energetic properties of propellants, which enhanced the propellant enthalpy variable and burn rate. Based on the AP optimized laser ablation, the optimal single-pulse impulse (I)~9.8 μN·s, specific impulse (Isp)~234.9 s, impulse coupling coefficient (Cm)~62.43 dyne/W and energy factor (η)~71.2% were obtained in 200 µm scale combustion chamber. This work would enable further improvements in the small volume and high integration of liquid propellant laser micro-thruster.

Evaluation of phthalic acid tri-ethylene diamine (TED) and folic acid-based carbon quantum dots for the detection of heavy metals in water resources using fibre-optic instrumentation

ABSTRACT Heavy metal pollution and toxicity from water resources have remained a great concern for the entire population. This research demonstrates the capability of carbon quantum dots (CQDs) for fluorescence-based heavy metal detection in different water resources using a fibre-optic spectrometer device. Two different types of CQDs phthalic acid and triethylenediamine (PT CQDs) and Folic acid (FCQDs) were synthesized using microwave irradiation and hydrothermal method, respectively. CQDs were characterized using several techniques such as TEM, EDX, XPS and FTIR. PTCQD and FCQDs both were tested for sensing capability in water reservoirs like household and river water. The results indicate that both CQDs were able to detect all six heavy metal ions (Pb2+, Co2+, Mn3+, Hg2+, Ni2+, Cr3+) tested in the study in the range of 0–100 µM. It was found that FCQDs show a three-fold higher sensitivity and greater resolution than PTCQDs for all the heavy metals samples. The CQDs’ sensing capability shows that they can achieve a limit of detection in the range of 0.15–3 µM along with 100% accuracy in terms of recovery with minimal error, these results indicate that both CQDs have a tremendous potential to be used as a sensor for the detection of heavy metals even in complex water matrices. FCQDs show more sensitivity for all metals compared to PTCQDs and used in future as a sensing tool for heavy metal detection with better sensitivity and accuracy with less response time.

Investigation of structure and soot formation in laminar inverse diffusion flames by atomic ratio measurements using laser-induced breakdown spectroscopy

This experimental study reports the two-dimensional C/O and H/O atomic ratio distributions of oxy-ethylene laminar inverse diffusion flames (IDFs) with elevated stoichiometric mixture fractions (Zst) using laser-induced breakdown spectroscopy (LIBS), and investigates the effects of Zst on the structure and soot formation of IDFs. The LIBS diagnostic system consisting of a pulsed Nd: YAG laser and a fiber optic spectrometer measures the atomic ratios of IDFs with Zst of 0.2–0.5, and the influence of laser energy on atomic ratio calibrations and measurements is corrected to improve accuracy. IDFs are divided into five zones, namely the oxidant zone, the chemiluminescence zone, the gap, the soot zone, and the fuel zone. The C/O atomic ratio of the chemiluminescence zone and the gap remains 0.35–0.5, and the soot zone is 0.4–0.7. Except for the gap, where the H/O atomic ratio remains at 0.55–0.60, the H/O atomic ratio of all other zones is greatly affected by Zst. These atomic ratio results demonstrate that the C/O atomic ratio has the advantage of differentiating the structure of IDFs. Experimental results show a C/O atomic ratio of 0.5–0.6 is required for soot inception in IDFs, so the elevated Zst delays soot inception by lowering the C/O atomic ratio near the flame sheet, and it also compresses the residence time and C/O atomic ratio space favorable for soot formation. Additionally, the decreased local equivalence ratio determined from the H/O atomic ratio further confirms that the increase of Zst makes IDFs unsuitable for soot formation. This study proves that LIBS is an effective flame diagnostic tool and the atomic ratios hold promise for studying a broader range of flame configurations.

Research on aluminum agglomeration characteristics of Al/NEPE propellant

Adding aluminum particles to solid propellants is used to improve the energy density of the propellant and the specific impulse of the engine. However, the aluminum particles will agglomerate to form large-sized condensed combustion products, which can cause nozzle erosion and two-phase flow loss. Therefore, it is necessary to study the aluminum agglomeration characteristics of solid propellants. In this paper, the combustion process of the Al/NEPE propellant was recorded by a high speed camera and a fiber optic spectrometer, and the condensed combustion products of the propellant were collected. The microstructure of the condensed combustion products was analyzed by a scanning electron microscope coupled with energy dispersive (SEM-EDS). These results show that the agglomeration process of aluminum particles may go through three stages: accumulation, aggregation and agglomeration. The condensed combustion products are mainly divided into aluminum agglomerates and smoke oxide particles. Generally, the size of agglomerates exceeds 50 μm, while the size of smoke oxide particles is less than 1 μm.

Correlation between chemical characteristics and optical spectra of Spirulina commercially available on the Bulgarian market

The aggregate of various chemical substances useful for the functioning of the human body are known as nutrients. Spirulina has been present in human nutrition since ancient times, but in recent years the interest in it has been particularly increased due to the emergence of numerous alternative methods of nutrition. This study aimed to compare the functional and elemental composition as well as the optical properties of commercial Spirulina products available on the Bulgarian market. For this purpose, fluorescence spectroscopy in the ultraviolet and visible range, fourier transform infrared spectroscopy and inductively coupled plasma optical emission spectroscopy were used. The basic components of the analyzed Spirulina samples are proteins (1657 and 1537 cm-1) and carbohydrates (1069 and 1054 cm-1) and no meaningful differences between the IR spectra of the samples. Concentrations of important microelements Mg, Fe, Cu, Zn, and Mn varies with the manufacturer. The highest levels for Mg (6.69 g kg-1) were measured in samples from USA, while the Spirulina fabricated in Bulgaria exhibits the highest contents of Zn (242 mg kg-1) and Cu (25.4 mg kg-1). All samples followed the tendency Mg&amp;gt;Fe&amp;gt;Mn&amp;gt;Zn&amp;gt;Cu. Making use of a fiber optic spectrometer the fluorescence spectra of the studied samples of Spirulina platensis for an excitation wavelength of 380 nm were measured. In these spectra we observe three fluorescence maxima: at 465 nm – nicotinamide dinucleotide phosphate, 640 nm chlorophyll a, and 736 nm due to similar to chlorophyll pigments. A strong positive correlation between the contents of Zn and Cu on the one side and the second fluorescence peak (λ=640 nm) for excitation wavelength at 380 nm. In contrast, a high negative correlation for Fe and the third fluorescence maximum (λ= 736nm) is observed for all excitation wavelengths. The correlation dependencies were obtained with the least squares method with a significance level of p ≤ 0.05.

Optical-Quality Assessment of a Miniaturized Intraocular Telescope.

Age-related macular degeneration (AMD) causes severe vision impairments, including blindness. An option to improve vision in AMD patients is through intraocular lenses and optics. Among others, implantable miniaturized telescopes, which direct light to healthy lateral regions of the retina, can be highly effective in improving vision in AMD patients. Yet, the quality of the restored vision might be sensitive to the optical transmission and aberrations of the telescope. To shed light on these points, we studied the in vitro optical performance of an implantable miniaturized telescope, namely, the SING IMT™ (Samsara Vision Ltd., Far Hills, NJ, USA) designed to improve vision in patients affected by late-stage AMD. Specifically, we measured the optical transmission in the spectral range 350-750 nm of the implantable telescope with a fiber-optic spectrometer. Wavefront aberrations were studied by measuring the wavefront of a laser beam after passing through the telescope and expanding the measured wavefront into a Zernike polynomial basis. Wavefront concavity indicated that the SING IMT™ behaves as a diverging lens with a focal length of -111 mm. The device exhibited even optical transmission in the whole visible spectrum and effective curvature suitable for retinal images magnification with negligible geometrical aberrations. Optical spectrometry and in vitro wavefront analysis provide evidence supporting the feasibility of miniaturized telescopes as high-quality optical elements and a favorable option for AMD visual impairment treatments.

Molecular Dispersion Spectroscopy Using a Code-Division-Multiplexed Optical Carrier

A fiber-optic molecular dispersion spectrometer using code-division multiplexing to make simultaneous phase measurements of a hydrogen cyanide (${\mathrm{H}}^{13}{\mathrm{C}}^{14}\mathrm{N}$) $2{\ensuremath{\nu}}_{3}$-band P10 rovibrational transition at multiple optical frequencies is demonstrated. A second-derivative anomalous dispersion response is digitally synthesized from sets of these concurrent measurements. The synthesized measurement demonstrates 3 orders of magnitude noise suppression relative to individual measurements, has intrinsic wavelength tuning linearization, and a spectroscopic detection limit of $146\phantom{\rule{0.2em}{0ex}}\mathrm{ppb}\phantom{\rule{0.1em}{0ex}}\mathrm{m}/\sqrt{\mathrm{Hz}}$.

Use of a fiber optic spectrometer to assess the minimum number of malignant cells by diffuse reflectance spectra in the near infrared region

Use of a fiber optic spectrometer to assess the minimum number of malignant cells by diffuse reflectance spectra in the near infrared region

Near-infrared normal spectral emissivity of molten Fe-Ni alloys by electromagnetic heating

The spectral emissivity of molten Fe-Ni alloys is especially critical to analysis the performance and quality of alloy. The near-infrared normal spectral emissivity of molten Fe-Ni alloys was measured at 1000–1600 nm in the temperature range of 1690–1845 K by a self-built measurement apparatus using the electromagnetic heating technology. The measurement apparatus mainly consists of the electromagnetic heating furnace, blackbody, optical fiber spectrometer and colorimetric thermometer. The dependence of near-infrared normal spectral emissivity of Fe-Ni alloys (Ni, Fe10Ni90, Fe30Ni70, Fe50Ni50, Fe70Ni30, Fe90Ni10 and Fe) on wavelength, temperature and composition were systematically investigated. The results show that the emissivity of Fe70Ni30 is higher in the iron-rich area, while the emissivity of Fe30Ni70 is the lowest in the nickel-rich area. Comparison of the measured and simulated results show that the emissivity of molten Fe-Ni alloys is reliable. The emissivity of Fe-Ni alloys provides reliable data for the research of alloys properties.

Spectrum diagnosis and temperature monitoring of femtosecond laser laminectomy

Orthopedic diseases are increasingly becoming a prominent problem threatening human health. Traditional mechanical osteotomy causes mechanical and thermal damages, which are believed to increase the safety risk of orthopedic surgery. Femtosecond lasers provide a safe and efficient method for laminectomy. In this study, the experiments were conducted on femtosecond laser ablation operations aided by convolutional neural network and collaborative control. The various spectra during femtosecond laser bone ablation were detected by using isolated porcine ribs. An optical fiber spectrometer was used to monitor the spectrum, which was proved to reflect the laser ablation process. The spectral composition during femtosecond laser bone ablation was analyzed. The second harmonic was related to the penetration. The temperature distribution indicated that 15 W with cooling was the best parameter for preventing carbonization. Defocusing the laser improved safety because the ablated effect was very limited when the defocus distance was 4 mm. Although large energy input resulted in better efficiency, it also caused carbonization due to overheating.

Optical Fiber Grating-Prism Fabrication by Imprint Patterning of Ionic-Liquid-Based Resist.

We present a method of microstructure fabrication on the tip of the optical fiber using a UV soft-imprint process of polymerizable ionic liquid-based optical resist. Ionic liquid with two UV-sensitive vinylbenzyl groups in the structure was diluted in non-hazardous propylene glycol (PG) to obtain liquid material for imprinting. No additional organic solvent was required. The impact of propylene glycol amount and exposure dose on optical and mechanical properties was investigated. The final procedure of the UV imprint on the optical fiber tip was developed, including the mold preparation, setup building, UV exposure and post-laser cure. As the IL-containing vinylbenzyl groups can also be polymerized by the radical rearrangement of double bonds through thermal heating, the influence of the addition of 1-2% BHT polymerization inhibitor was verified. As a result, we present the fabricated diffraction gratings and the optical fiber spectrometer component-grism (grating-prism), which allows obtaining a dispersion spectrum at the output of an optical in line with the optical fiber long axis, as the main component in an optical fiber spectrometer. The process is very simple due to the fact that its optimization already starts in the process of molecule design, which is part of the trend of sustainable technologies. The final material can be designed by the tailoring of the anion and/or cation molecule, which in turn can lead to a more efficient fabrication procedure and additional functionalities of the final structure.

Fast Emissivity Measuring Apparatus With Adjustable Focusing and Field Calibration

A fast emissivity measuring apparatus in the range of 1.4-2.5 μm with adjustable focusing and field calibration has been developed in this paper. Benefiting from the portable, fast and efficient characteristics of the fiber optic spectrometer, the rapid in-situ emissivity measurement in industry, such as aluminum profile casting or molten-salt monitoring, can be realized by this apparatus. The lightpath system of this apparatus is designed based on the principle of the Newtonian reflecting telescope, and the relationship between the radiation signal and the object distance is analyzed in detail. The focus adjustment of the apparatus improves the radiation entering the system, thus ensuring that the measurement signal does not decrease rapidly with the increase of distance. The emissivity of silicon carbide and pure silicon is calculated by the Fresnel formula and the results of measured emissivity by the apparatus are in good agreement with the data of theoretical calculation, which verifies the reliability of the apparatus. The maximum error of calibrated radiation of this apparatus is not more than 2.5%, and the average error is less than 1% in the wavelength range of 1.4-2.5 μm. In a feasibility test, the relative combined uncertainty of the spectral emissivity of silicon carbide is less than 5.73%.

Portable determinations for legislated dissolved nitrogen forms in several environmental water samples as a study case

In this work, we have studied the main species involved in determining total dissolved nitrogen (TDN) in water samples for accommodating a variety of quantitation methodologies to portable instruments and with the goal to achieve in situ analysis. The rise of water eutrophication is becoming an ecological problem in the world and TDN contributes markedly to this. Traditionally the several forms of DN are measured in the laboratory using conventional instrumentation from grab samples, but their analysis in place and in real time is a current demand. Inorganic nitrogen: NO3−, NO2− and NH4+, and organic nitrogen, such as amino nitrogen were tested here. For nitrate that presents native UV absorption suitable for direct water analysis, a portable optical fiber probe was compared with benchtop equipment and an in place analyzer. For nitrate, nitrite and ammonium, in situ solid devices that deliver reagents needed were tested and water color was measured by a smartphone coupled with a miniaturized optical fiber spectrometer and a miniaturized spectrometer or from images obtained and their RGB components. Amino nitrogen of some aromatic aminoacids with native fluorescence was followed by a portable optical fiber probe. Organic amino nitrogen and ammonium were determined by a portable luminometer and luminol supported in a measurement tube. Moreover, a portable miniaturized liquid chromatograph was shown suitable for monitoring priority nitrogen environmental pollutants. All options provided suitable results in comparison with lab estimations and were useful for evaluating if the legislation is fulfilled for the variety of tested waters. A discussion about the several portable options proposed for in place analysis, in function of the legislated determinations needed for each type of water was carried out.

Direct emission spectrometry determination of fluorine in carbon materials: Argon dc arc and spark radiation sources

In this work, the procedure for direct atomic emission spectrometry (AES) determination of fluorine impurities in carbon materials was proposed. Two types of simple radiation sources with direct solid (powdered) sample introduction were studied: direct current arc (25A) and high-power low voltage spark (300 V, of 2348 μF). For each source, standard graphite extra high purity electrodes and argon discharge atmosphere were used. Red spectral region approach to non-metal AES determination was employed with analytical line F I 685.603 nm. The spectra were registered by compact tunable fiber-optic spectrometer with linear complementary metal oxide semiconductor array (CMOS) sensor and short-focus lens. Special measures were taken to counter red spectral region interferences, such as CN molecular bands and thermal radiation. The excitation of F in both types of radiation source was studied. A set of artificial graphite and NaF based standards was prepared for calibration and evaluated by two independent approaches: indirect dc arc AES and water extraction photometry. Limit of detection was determined for dc arc source was 5 μg/g, and for spark 20 μg/g of F. The whole cycle of measurement with each type of radiation source takes 10 min. As the power of dc arc is limited by generator capabilities, it is possible that even lower limit of detection is achievable with higher discharge current.

Development of fiber optic in vitro release testing method for dexamethasone release from the oil solutions.

For many parenteral drugs, there is still no standardized method for in vitro release (IVR) testing available. This article presents the development of a new IVR method for oil solutions using a dialysis membrane and USP II apparatus coupled to a fiber optic UV-Vis spectrometer. Experiments were performed using dexamethasone formulations containing castor oil as a solvent with the addition of cosolvents, 20 % (v/v) of isopropanol or Capryol® 90. Based on solubility testing results, castor oil was chosen as the best solvent amongst other vegetable oils, while a significant increase in solubility was obtained by adding either of the two cosolvents. Partitioning experiments were performed to ensure these formulations could achieve prolonged drug release. IVR testing was performed with model formulations and critical test parameters were varied in order to examine the method's sensitivity. The developed method was sensitive to temperature and stirring rate, while coupling the USP II apparatus with a fiber optic UV-Vis spectrometer enabled complete automation. Moreover, due to the interference of excipients on fiber optic detection of dexamethasone during the release testing, derivative spectroscopy was successfully introduced for the elimination of the interference. The developed IVR method described herein could be useful in preformulation investigations and the early development of novel formulations.