Long-wave infrared detection based on difference-frequency generation up-conversion.

Imaging human brown adipose tissue under room temperature conditions with 11C-MRB, a selective norepinephrine transporter PET ligand

The complete destruction of separate mixtures of 1.1 mM 4-chlorophenol (aqueous) and 0.61 mM pentachlorophenol (aqueous slurry) take place in the presence of 0.5 g of iron particles in 10 mL of 0.32 mM ethylenediaminetetraacetic acid (EDTA) under ambient air under room temperature conditions. Under this reaction condition, the time required to reach complete disappearance to the detection limit of GC-FID for each compound was 4 h for 4-chlorophenol and 70 h for pentachlorophenol. Electrospray ionization mass spectral (ESI-MS) analysis of the 4-chlorophenol reaction mixture after its complete disappearance indicated non-chlorinated, primarily low molecular weight products; however, Cl- from 4-chlorophenol was not detected due to adsorption onto the iron or its corrosion products. Radical trap and control experiments suggest that the mechanism for destruction initiates with dioxygen activation, leading to the formation of reactive oxygen species (ROS) and ultimately ring opening of the phenolic compounds. This is the first example of an abiotic system capable of the complete destruction of an organic pollutant under room temperature and pressure conditions through dioxygen activation chemistry.

We describe development of spectrally tunable micro-engineered filters operating in the longwave infrared (LWIR) from 8 to 12 micron based on the guided mode resonance (GMR) phenomenon. The device structure consists of a subwavelength dielectric grating on top of a planar waveguide using high index dielectric transparent materials, i.e., germanium (Ge) with a refractive index of 4.0 and zinc selenide (ZnSe) with refractive index of 2.4. The filters are designed to reflect incident broadband light at one (or more) narrow spectral band while fully transmitting the other wavelengths. Tuning of the reflection wavelength is achieved by changing the angle of incidence of light by mechanically tilting the filter. Filters based on one dimensional (1-D) gratings are polarization dependent and those based on two dimensional (2-D) gratings are less sensitive to incident polarization of light. Both filters were fabricated using standard dielectric deposition and photolithographic techniques and characterized. Simple 2-layer anti-reflection coatings were applied to improve transmission over the entire spectral region. Our experimental setup consists of a modified commercial Fourier Transform Infrared Spectrometer (FTIR) system with a separate chamber for a collimated incident beam of light, focusing optics, a liquid-nitrogen-cooled mercury cadmium telluride (MCT) detector, a wire grid polarizer and a micro-engineered filter. We will present detailed characterization experiment and compare the theoretical and experimental results.

Objective: The aim of this study was to determine the thermal effects of diode laser irradiation on titanium implants. Methods: An implant (3.5 × 11 mm) was placed into a bovine bone block. A three-wall intrabony defect was created to simulate peri-implant defect. Two thermocouples were secured to the apical and coronal surfaces to measure temperature changes (ΔT) during irradiation. The block was placed in a 37°C water bath and at room temperature (21°C). The defect was irradiated with different diode lasers (fiber 300 μm), while the coronal part of the implant was slightly emerging from the water. While the laser tip was positioned parallel to the implant, the defect was irradiated for 30 sec at 2 W in continuous and pulsed mode. Twenty laser irradiations were performed for each laser wavelength for assessment of ΔT. The linear mixed model was used for comparative statistics. Results: The 980 nm pulsed laser resulted in the highest ΔT (°C) at the coronal (22.45 ± 2.1/14.15 ± 0.13) and apical level (5.4 ± 0.56/3.56 ± 0.35) when this laser was used in both room temperature and water bath conditions, respectively. Similarly, highest ΔT (p < 0.0001) for the 810 nm was 14.3 ± 1.6/12.51 ± 0.63 and apical 3.42 ± 0.52/2.58 ± 0.25, for the 970 nm was 13 ± 1.4/9.93 ± 0.47 and apical 2.89 ± 0.19/2.01 ± 0.19 compared to the 940 nm laser coronally 10.1 ± 0.6/9.19 ± 0.35 and apically 1.67 ± 0.34/1.80 ± 0.17. The coronal part of the implant surpassed the critical threshold of 10°C when irradiated with each of the lasers in the room temperature conditions. Conclusions: Within the limitations of the study, the 940 nm laser seems to control better the risks of overheating during implant irradiation.

Eggs that have been hard-boiled are frequently used as ready-to-eat food. Refrigerated and frozen storage of hard-boiled eggs causes issues, such as customer rejection owing to textural changes. The objective of this research is to ascertain how storage temperature affects hard-boiled eggs' alteration in texture over time. Medium-sized brown shell eggs were acquired from a local market, boiled at 100°C for 15 min, and then stored at room temperature (25°C), refrigeration (4°C), and freezing (-18°C) conditions for 0, 12, 24, and 48 h. Fourier transform infrared spectroscopy (FTIR), texture profile, visual observation using a gemological microscope, free amino acid content, and color were measured. Freezing had a substantial impact on the eggs' hardness, gumminess, chewiness, and cohesiveness (p<0.05). The FTIR spectrums confirmed the textural changes in bonds of amide A (3,271 cm-1), amide I (1,626.2 cm-1), amide II (1,539.0 cm-1), C=O stretch of COO- (1,397 cm-1), asymmetric PO2- stretch (1,240 cm-1). Microscopic images confirmed structural changes in eggs stored at -18°C. The free amino acid content was lower in fresh and frozen eggs than in the rest (p<0.05). However, there was no discernible variation in the egg white's color when eggs were kept at 4°C (p>0.05). Salmonella spp. was found exclusively in eggs kept at room temperature. In conclusion, hard-boiled eggs did not exhibit structural or chemical changes when stored at 4°C for up to 48 h compared to freezing and room temperature conditions.

Uncooled long‐wave infrared (LWIR) detectors substantially facilitate the advancement of miniaturized, highly integrated, and lightweight human radiation perception technology. However, constrained by materials and device structures, the progress of conventional LWIR detectors has stagnated in efficiently detecting weak human radiation at room temperature. Herein, a pyroelectric photogating‐based uncooled LWIR detector with a graphene‐Al2O3‐LiNbO3 hybrid structure is proposed for highly sensitive human radiation detection. The device leverages the polarized charge of LiNbO3 to modulate the conductance carriers in graphene, thereby achieving an amplified photoresponse in the LWIR range of 8 to 11 µm. Notably, at room temperature, the device exhibits a superior responsivity of 48 A W−1 under blackbody radiation, surpassing the performance of previous 2D materials‐based LWIR detectors. Remarkably, it can identify the radiation signals of a human finger, a feat previously considered challenging for devices relying on graphene or other 2D materials. These results reveal the potential of pyroelectric photogating and provide valuable insights for developing high‐sensitivity, uncooled photodetectors.

The mid- and long-wave infrared point spectrometer (MLPS) is an infrared point spectrometer that utilizes unique technologies to meet the spectral coverage, spectral sampling, and field-of-view (FOV) requirements of many future space-borne missions in a small volume with modest power consumption. MLPS simultaneously acquires high resolution mid-wave infrared (∼2-4 µm) and long-wave infrared (∼5.5-11 µm) measurements from a single, integrated instrument. The broadband response of MLPS can measure spectroscopically resolved reflected and thermally emitted radiation from a wide range of targets and return compositional, mineralogic, and thermophysical science from a single data set. We have built a prototype MLPS and performed end-to-end testing under vacuum showing that the measured spectral response and the signal-to-noise ratio (SNR) for both the mid-wave infrared (MIR) and long-wave infrared (LIR) channels of MLPS agree with established instrument models.

This study investigated the influence of room temperature on the final prototype parts produced using the fused deposition modeling (FDM) technique. Real-time room temperature data was collected using a wireless sensor with a time series data collection method. A data-driven model called Long Short-Term Memory (LSTM) network was developed to predict room temperature. The model was trained using data from the wireless sensors collected during the experimental procedure, which involved printing prototype parts in different seasons of the year. The developed LSTM network demonstrated its capability to accurately predict temperature, enabling the detection of printing defects under various room temperature conditions. The study revealed that lower room temperatures had a more significant impact on the surface roughness of the printed parts compared to higher room temperatures. The effectiveness of the developed model was confirmed by comparing its results with the experimental data using Root Mean Square Error (RMSE). The developed LSTM model found an RMSE of 0.003993 for predicting cold room temperature data and an RMSE of 0.033993 for predicting hot temperature data. The developed LSTM model offers a valuable tool for detecting printing defects in different room temperature conditions. It provides users with information about the room temperature necessary for printing high-quality parts, thereby enhancing the printing process capability and minimizing defect issues in the printed parts.

Strong smog penetrating capability of quantum cascade laser at 8.9 micrometre

The trade-off between spectral resolution and instrument throughput is analyzed for a compact, uncooled, longwave infrared (LWIR) channeled spectropolarimeter (IRCSP). The IRCSP was developed as a part of the Sub-mm Wave and InfraRed Polarimeters (SWIRP) project out of NASA's Goddard Spaceflight Center. The IRCSP scientific objective targets measurements of AOLP and DOLP with 1-µm spectral resolution from 8.5 - 12.5µm in a single snapshot. The geometry of the field stop determines the field of view (FOV) of the IRCSP. This work relates the spectral resolution, instrument throughput, and polarimetric accuracy of a spectro-polarimeter to the FOV. The accuracy of linear Stokes retrievals for low temperature thermal targets are predicted for varying FOV and measurement noise conditions. This work presents a method to quantify the achievable accuracy in AOLP and DOLP as a function of field stop dimensions and signal-to-noise ratio (SNR). While smaller field stops are shown to improve accuracy as the spectral resolution is increased, low SNR is the dominant source of error for the IRCSP prototype. For the IRCSP, a SNR of at least 80 is required to produce DOLP measurements with < 5% error for targets with DOLP < 0.2.

The Infrared Microspectroscopy Beamline at the Australian Synchrotron is equipped with a Fourier transform infrared (FTIR) spectrometer, which is coupled with an infrared (IR) microscope and a choice of two detectors: a single-point narrow-band mercury cadmium telluride (MCT) detector and a 64 × 64 multi-pixel focal plane array (FPA) imaging detector. A scanning-based point-by-point mapping method is commonly used with a tightly focused synchrotron IR beam at the sample plane, using an MCT detector and a matching 36× IR reflecting objective and condenser (NA = 0.5), which is time consuming. In this study, the beam size at the sample plane was increased using a 15× objective and the spatio-spectral aberrations were investigated. A correlation-based semi-synthetic computational optical approach was applied to assess the possibilities of exploiting the aberrations to perform rapid imaging rather than a mapping approach.

The development of a scalable, low cost, low power, and room temperature operating detector technology capable of high spatial resolution imaging over IR bands of interest can advance and extend space and satellite sensing capabilities such as remote sensing and earth observation. Conventional infrared (IR) band photodetectors based on HgCdTe material operating over short-wave infrared (SWIR), mid-wave infrared (MWIR), and/or long-wave infrared (LWIR) bands often require external cooling to achieve high performance IR sensing and imaging. By integrating bilayers of doped graphene to function as a high mobility channel to aid the recombination of photogenerated carriers, a graphene-enhanced IR photodetector with HgCdTe absorbing layer can be developed providing high performance uncooled detection over SWIR, MWIR, and LWIR (~1.3-14 &mu;m) bands. Development of the high-performance IR photodetector technology involves ptype doping of graphene bilayers deposited on Si/SiO₂ with boron using a spin-on dopant (SOD) process, and then transfer of the doped bilayer graphene onto HgCdTe substrates. The graphene-enhanced HgCdTe SWIR/MWIR/LWIR band detectors were analyzed and characterized material and optoelectronically to demonstrate high performance IR detection at room temperature for advanced NASA Earth Science, defense, and commercial applications.

Thermal comfort and self-reported productivity in an office with ceiling fans in the tropics

Trade-off studies on spectral coverage, signal-to-noise ratio (SNR), and spectral resolution for a hyperspectral infrared (IR) sounder on a geostationary satellite are summarized. The data density method is applied for the vertical resolution analysis, and the rms error between true and retrieved profiles is used to represent the retrieval accuracy. The effects of spectral coverage, SNR, and spectral resolution on vertical resolution and retrieval accuracy are investigated. The advantages of IR and microwave sounder synergy are also demonstrated. When focusing on instrument performance and data processing, the results from this study show that the preferred spectral coverage combines long-wave infrared (LWIR) with the shorter middle-wave IR (SMidW). Using the appropriate spectral coverage, a hyperspectral IR sounder with appropriate SNR can achieve the required science performance (1 km vertical resolution, 1 K temperature, and 10% relative humidity retrieval accuracy). The synergy of microwave and IR sounders can improve the vertical resolution and retrieval accuracy compared to either instrument alone.

MODIS is one of the key instruments for the NASA's EOS mission, currently operated on both Terra and Aqua spacecraft making continuous and complementary observations in 36 spectral bands from 0.4 to 14.2 micrometers. Among them are long-wave infrared (LWIR) bands (11-14.2 micrometers) with Photoconductive (PC) HgCdTe detectors. The Terra MODIS pre-launch thermal vacuum calibration and characterization have shown clear evidence of an optical leak presented by the 11 micron band (band 31) into other PC bands (bands 32-36). A correction algorithm has been designed and implemented in the MODIS Level 1B (L1B) code using coefficients determined from the lunar observations made in year 2000. In this work we evaluate the optical leak correction coefficients derived from Terra MODIS lunar observations from January 2001 to December 2004. Our method assumes that in the absence of an optical leak the detector's signal would decay away from its peak response to the moon as an inverse power series function of the frame offset number. The least Chi-squared minimization method is used to calculate the parameters in the fitting function. Analysis results from the lunar and Earth view observations show that the Terra MODIS PC optical leak has been effectively removed. The Level 1B algorithm has been shown to be stable.