Mixture fraction measurement in turbulent non-premixed MILD jet flame using Rayleigh scattering.

Turbulent combustion of jet flames in a hot diluted coflow of combustion products is conducive to the transition from conventional flamelet combustion to a regime of moderate or intense low oxygen dilution (MILD) combustion, which is commonly characterized by a very low emission and noise. MILD combustion is also characterized by distributed combustion where the net heat release is positive across the entire combustion domain. The turbulence/chemistry interactions in this regime that determine the flame structure, local temperature, and species distribution critically depend on the mixture fraction and scalar dissipation fields. However, there are no experimental tools to measure the mixture fraction field in a distributed (MILD) combustion regime. The present work offsets this limitation by demonstrating a Rayleigh scattering-based approach to measure mixture fraction in a turbulent ethylene MILD combustion zone. 1D counterflow flame simulations enabled mapping the locally calibrated Rayleigh scattering fields to mixture fractions in the fuel-rich regions. This approach also shows very low sensitivity to the local temperature and composition. Overall, the results provide compelling evidence that the distributed heat release does not significantly impact the turbulent processes of the flow-field for the conditions examined. The measurement uncertainty from this approach and its extension to more complex fuels are also discussed. The present technique is limited to mildly turbulent, fully MILD/distributed flame with representative scalar dissipation rates.

Dehydroepiandrosterone (DHEA) role in enhancement and maintenance of implantation (DREAM): randomised double-blind placebo-controlled trial-study protocol.

INTRODUCTION: Dehydroepiandrosterone (DHEA) is an important precursor of androgen and has been studied and researched extensively for improving the various outcome measures of ovarian stimulation in women with advanced age or poor ovarian response. Androgens also play an important role in the enhancement of endometrial and decidual function by regulating both the transcriptome and secretome of the endometrial stromal cells and have a positive effect on various factors like insulin-like growth factor binding protein 1, homeobox genes (HOXA10, HOXA11), secreted phosphoprotein 1, prolactin which are necessary for implantation. It is well-known that the circulating 'precursor pool' of DHEA declines with age more so in poor ovarian reserve patients and exogenous supplementation may be beneficial in such cases. This double-blinded randomised controlled trial (RCT) aims to test the hypothesis whether transient targeted supplementation of DHEA as an adjuvant to progesterone in frozen embryo transfer (FET) cycles, for women with low serum testosterone, helps in improving live birth rate. METHODS AND ANALYSIS: This study is planned as a double-blinded, placebo-controlled randomised trial and the sample size, calculated for the primary outcome measure-live birth rate, is 140. All participants will be having a flexible antagonist protocol for controlled ovarian stimulation and an elective freeze-all policy for the embryos as per the hospital protocol after written informed consent. For FET, the endometrium will be prepared by hormone replacement treatment protocol. During the FET cycle, the intervention group will be receiving DHEA 25 mg two times a day for 15 days from the day of starting progesterone supplementation and the control group will be receiving a placebo. ETHICS AND DISSEMINATION: The approval of the study was granted by the Clinical Trials Registry-India and the Institutional Ethical Committee of CRAFT Hospital and Research Center. All participants will provide written informed consent before being randomised into allocated treatment groups. The results will be disseminated to doctors and patients through conference presentations, peer-reviewed publications, social media and patient information booklets. TRIAL REGISTRATION NUMBERS: CTRI/2020/06/025918; ECR/1044/Inst/KL/2018.

The loss of carbon dioxide from activated perbenzoate anions in the gas phase: unimolecular rearrangement via epoxidation of the benzene ring.

The unimolecular reactivities of a range of perbenzoate anions (X-C6H5CO3-), including the perbenzoate anion itself (X = H), nitroperbenzoates (X = para-, meta-, ortho-NO2), and methoxyperbenzoates (X = para-, meta-OCH3) were investigated in the gas phase by electrospray ionization tandem mass spectrometry. The collision-induced dissociation mass spectra of these compounds reveal product ions consistent with a major loss of carbon dioxide requiring unimolecular rearrangement of the perbenzoate anion prior to fragmentation. Isotopic labeling of the perbenzoate anion supports rearrangement via an initial nucleophilic aromatic substitution at the ortho carbon of the benzene ring, while data from substituted perbenzoates indicate that nucleophilic attack at the ipso carbon can be induced in the presence of electron-withdrawing moieties at the ortho and para positions. Electronic structure calculations carried out at the B3LYP/6-311++G(d,p) level of theory reveal two competing reaction pathways for decarboxylation of perbenzoate anions via initial nucleophilic substitution at the ortho and ipso positions, respectively. Somewhat surprisingly, however, the computational data indicate that the reaction proceeds in both instances via epoxidation of the benzene ring with decarboxylation resulting--at least initially--in the formation of oxepin or benzene oxide anions rather than the energetically favored phenoxide anion. As such, this novel rearrangement of perbenzoate anions provides an intriguing new pathway for epoxidation of the usually inert benzene ring.

The fragmentation pathways of protonated Amiton in the gas phase: towards the structural characterisation of organophosphorus chemical warfare agents by electrospray ionisation tandem mass spectrometry.

Amiton (O,O-diethyl-S-[2-(diethylamino)ethyl] phosphorothiolate), otherwise known as VG, is listed in schedule 2 of the Chemical Weapons Convention (CWC) and has a structure closely related to VX (O-ethyl-S-(2-diisopropylamino)ethylmethylphosphonothiolate). Fragmentation of protonated VG in the gas phase was performed using electrospray ionisation ion trap mass spectrometry (ESI-ITMS) and revealed several characteristic product ions. Quantum chemical calculations provide the most probable structures for these ions as well as the likely unimolecular mechanisms by which they are formed. The decomposition pathways predicted by computation are consistent with deuterium-labeling studies. The combination of experimental and theoretical data suggests that the fragmentation pathways of VG and analogous organophosphorus nerve agents, such as VX and Russian VX, are predictable and thus ESI tandem mass spectrometry is a powerful tool for the verification of unknown compounds listed in the CWC.