Diagnostic Aspects of Paraquat in the Forensic Toxicology: A Systematic Review.

Background: Paraquat (N, N-dimethyl-4,4-bipyridinium dichloride) is a nonselective, fast-acting, and contact chemical herbicide used extensively for weed control. It has high acute oral toxicity, the ability to accumulate in the lungs, and a high potential for pulmonary fibrosis after its intoxication. The present systematic review focuses on evaluating diagnostic aspects of paraquat (PQ) in forensic toxicology. Methods: Evaluation of the literature according to the following criteria: only human studies published from February 1971 to March 2022 which are in English on the following databases: 1) Medline/PubMed/MeSH search words: ((Methyl viologen [Title/Abstract]) OR (paraquat [MeSH Terms])) AND (forensic [Title/Abstract]); 2) Scopus Keywords related to the study aim included forensic toxicology, paraquat, Methyl viologen; 3) Web of Science. Keywords related to the study aim included forensic toxicology, paraquat, and Methyl viologen. Results: Thirty full-text articles were included. The results of our review indicate plasma and urine are more used for identifying PQ, and liver, lung, and gastric fluid are important in postmortem cases. Preparation methods, including liquid-liquid extraction (LLE), solid-phase extraction, and acetonitrile-precipitated protein, are often required for removing interfering substances. Chromatographic methods, among other analytical techniques, are more sensitive, specific, and applicable. Conclusion: Our review suggests that plasma, urine, and lungs should be prioritized in sampling. Solid-phase extraction has better recovery than LLE in many samples. Colorimetric methods are not used much today, and radioimmunoassay (RIA) has limited application despite its high sensitivity. Gas and liquid chromatography methods appear to offer the best approach for the analysis of PQ.

Surface Phonon Polariton-Mediated Near-Field Radiative Heat Transfer at Cryogenic Temperatures.

Recent experiments, at room temperature, have shown that near-field radiative heat transfer (NFRHT) via surface phonon polaritons (SPhPs) exceeds the blackbody limit by several orders of magnitude. Yet, SPhP-mediated NFRHT at cryogenic temperatures remains experimentally unexplored. Here, we probe thermal transport in nanoscale gaps between a silica sphere and a planar silica surface from 77-300 K. These experiments reveal that cryogenic NFRHT has strong contributions from SPhPs and does not follow the T^{3} temperature (T) dependence of far-field thermal radiation. Our modeling based on fluctuational electrodynamics shows that the temperature dependence of NFRHT can be related to the confinement of heat transfer to two narrow frequency ranges and is well accounted for by a simple analytical model. These advances enable detailed NFRHT studies at cryogenic temperatures that are relevant to thermal management and solid-state cooling applications.

Quantitative Mapping of Unmodulated Temperature Fields with Nanometer Resolution.

Quantitative mapping of temperature fields with nanometric resolution is critical in various areas of scientific research and emerging technology, such as nanoelectronics, surface chemistry, plasmonic devices, and quantum systems. A key challenge in achieving quantitative thermal imaging with scanning thermal microscopy (SThM) is the lack of knowledge of the tip-sample thermal resistance (RTS), which varies with local topography and is critical for quantifying the sample temperature. Recent advances in SThM have enabled simultaneous quantification of RTS and topography in situations where the temperature field is modulated enabling quantitative thermometry even when topographical features cause significant variations in RTS. However, such an approach is not applicable to situations where the temperature modulation of the device is not readily possible. Here we show, using custom-fabricated scanning thermal probes (STPs) with a sharp tip (radius ∼25 nm) and an integrated heater/thermometer, that one can quantitatively map unmodulated temperature fields, in a single scan, with ∼7 nm spatial resolution and ∼50 mK temperature resolution in a bandwidth of 1 Hz. This is accomplished by introducing a modulated heat input to the STP and measuring the AC and DC responses of the probe's temperature which allow for simultaneous mapping of the tip-sample thermal resistance and sample surface temperature. The approach presented here─contact resistance resolved scanning thermal microscopy (CR-SThM)─can greatly facilitate temperature mapping of a variety of microdevices under practical operating conditions.

Near-field thermophotovoltaics for efficient heat to electricity conversion at high power density.

Thermophotovoltaic approaches that take advantage of near-field evanescent modes are being actively explored due to their potential for high-power density and high-efficiency energy conversion. However, progress towards functional near-field thermophotovoltaic devices has been limited by challenges in creating thermally robust planar emitters and photovoltaic cells designed for near-field thermal radiation. Here, we demonstrate record power densities of ~5 kW/m2 at an efficiency of 6.8%, where the efficiency of the system is defined as the ratio of the electrical power output of the PV cell to the radiative heat transfer from the emitter to the PV cell. This was accomplished by developing novel emitter devices that can sustain temperatures as high as 1270 K and positioning them into the near-field (<100 nm) of custom-fabricated InGaAs-based thin film photovoltaic cells. In addition to demonstrating efficient heat-to-electricity conversion at high power density, we report the performance of thermophotovoltaic devices across a range of emitter temperatures (~800 K-1270 K) and gap sizes (70 nm-7 µm). The methods and insights achieved in this work represent a critical step towards understanding the fundamental principles of harvesting thermal energy in the near-field.

Microwatt-Resolution Calorimeter for Studying the Reaction Thermodynamics of Nanomaterials at High Temperature and Pressure.

Calorimetry of reactions involving nanomaterials is of great current interest, but requires high-resolution heat flow measurements and long-term thermal stability. Such studies are especially challenging at elevated reaction pressures and temperatures. Here, we present an instrument for measuring the enthalpy of reactions between gas-phase reactants and milligram scale nanomaterial samples. This instrument can resolve the net change in the amount of gas-phase reactants due to surface reactions in an operating range from room temperature to 300 °C and reaction pressures of 10 mbar to 30 bar. The calorimetric resolution is shown to be <3 µW/√Hz, with a long-term stability <4 µW/hour. The performance of the instrument is demonstrated via a set of experiments involving H2 absorption on Pd nanoparticles at various pressures and temperatures. For this specific reaction, we obtained a mass balance resolution of 0.1 µmol/√Hz. Results from these experiments are in good agreement with past studies establishing the feasibility of performing high resolution calorimetry on milligram scale nanomaterials, which can be employed in future studies probing catalysis, phase transformations, and thermochemical energy storage.

Phononic thermal transport properties of C3N nanotubes.

Reverse nonequilibrium molecular dynamics (RNEMD) is employed to study the phononic thermal transport properties of C3N nanotubes. We study the effect of nanotube length and diameter on the thermal conductivity and investigate the phonon transport transition from ballistic to diffusive regime in C3N nanotubes. It is found that the thermal conductivity of C3N nanotubes is significantly lower than those of carbon nanotubes across the entire ballistic-diffusive range. In addition, significantly lower ballistic to diffusive transition length (72-80 nm) is observed in C3N nanotubes compared to carbon nanotubes. The inspection of phonon dispersion curves shows that carbon nanotubes have stiffer acoustic modes than C3N nanotubes which results in lower group velocities for C3N nanotubes. Due to the presence of nitrogen atoms, the phonon mean free paths and relaxation times of C3N nanotubes are shorter than those of the carbon nanotubes. The combined effect of lower group velocities and relaxation times leads to the lower thermal conductivity of C3N nanotubes.

Buprenorphine augmentation improved symptoms of OCD, compared to placebo - Results from a randomized, double-blind and placebo-controlled clinical trial.

BACKGROUND: In the search for new psychopharmacologic options in the treatment of obsessive-compulsive disorders (OCD), some findings suggested that augmentation with buprenorphine, a partial-opioid agonist used to treat opioid addiction, moderate acute pain and moderate chronic pain, is worthy of consideration. Accordingly, to explore this possibility further, a double-blinded, placebo-controlled clinical trial was performed. METHOD: A total of 43 patients (mean age: 34.41 years; SD = 6.58; 53.5% males) with refractory OCD and treated with SSRIs or clomipramine at therapeutic dosages were randomly assigned either to an adjuvant buprenorphine or to an adjuvant placebo condition. Patients completed the Yale-Brown-Obsessive-Compulsive Scale (Y-BOCS) at baseline, weeks 3, 9 and 12 (study completion). Buprenorphine (2-4 mg; sublingual) and placebo (tablets with identical shape, color, consistency, and scent) were given daily. RESULTS: Symptoms of obsessive-compulsive disorders decreased over time, but more so in the buprenorphine than in the placebo condition. Substantial improvements were observed up to week 3 and then 9. Response and partial response were observed in the buprenorphine at week 9 more than in the placebo condition. The advantage had disappeared by week 12. CONCLUSIONS: The pattern of results suggests that adjuvant buprenorphine augmentation can reduce symptoms of obsessive-compulsive disorders after only three weeks, compared to a placebo. Adjuvant buprenorphine seems to accelerate symptom improvement.