Revealing the Mechanism of Dioxin Formation from Municipal Solid Waste Gasification in a Reducing Atmosphere

Gasification is an effective technology for the thermal disposal of municipal solid waste (MSW) with lower dioxin emission compared to the prevailing incineration process. Nevertheless, the mechanism of dioxin formation in the reducing atmosphere during the gasification process was seldomly explored. Herein, the effects of the atmosphere, temperature, and chlorine source were systematically investigated in terms of dioxin distribution. With CO₂ and H₂O as gasification agents, a reducing reaction atmosphere was formed with abundant H₂ which effectively suppressed the generation of C-Cl, contributing to a substantial decrease of dioxin concentration by ∼80% compared to the incineration process. The formation of dioxin was favored at temperatures below 700 °C with its peak concentration achieved at 500 °C. It was unveiled that inorganic chlorine played a dominant role in the reducing atmosphere, with a lower proportion of C-O-C/O-C═O on residual slag compared to an oxidizing atmosphere. Additionally, the generated H₂ reduced the concentration of dioxins by attacking C-Cl and inhibiting the crucial Deacon reaction for dioxin formation, validated by density functional theory calculation. Eventually, the formation route paradigm and the reaction mechanism of dioxin formation from MSW gasification were revealed, facilitating and rationally guiding the control of dioxin emission.

[SARS-CoV-2 with transcription regulatory sequence motif mutation poses a greater threat]

OBJECTIVE

To analyze the mutations in transcription regulatory sequences (TRSs) of coronaviruss (CoV) to provide the basis for exploring the patterns of SARS-CoV-2 transmission and outbreak.

METHODS

A combined evolutionary and molecular functional analysis of all sets of publicly available genomic data of viruses was performed.

RESULTS

A leader transcription regulatory sequence (TRS-L) usually comprises the first 60-70 nts of the 5' UTR in a CoV genome, and the body transcription regulatory sequences (TRS-Bs) are located immediately upstream of the genes other than ORF1a and 1b. In each CoV genome, the TRS-L and TRS-Bs share a specific consensus sequence, namely the TRS motif. Any changes of nucleotide residues in the TRS motifs are defined as TRS motif mutations. Mutations in the TRS-L or multiple TRS-Bs result in superattenuated variants. The spread of super-attenuated variants may cause an increase in asymptomatic or mild infections, prolonged incubation periods and a decreased detection rate of the viruses, thus posing new challenges to SARS-CoV-2 prevention and control. The super-attenuated variants also increase their possibility of long-term coexistence with humans. The Delta variant is significantly different from all the previous variants and may lead to a large-scale transmission. The Delta variant (B.1.617.2) with TRS motif mutation has already appeared and shown signs of spreading in Singapore, which, and even the Southeast Asia, may become the new epicenter of the next wave of SARS-CoV-2 outbreak.

CONCLUSION

TRS motif mutation will occur in all variants of SARS-CoV-2 and may result in super-attenuated variants. Only super-attenuated variants with TRS motif mutations will eventually lose the abilities of cross-species transmission and causing outbreaks.

0853 Fetal Heart Rate Variability Increases During Maternal Sleep Apnea Events

Introduction

While studies have established that SDB during pregnancy increases the risk of adverse maternal outcomes, fetal effects are less well studied. Evidence suggests that fetal heart rate decelerations, an indicator of fetal distress, may be elicited by SDB. We examined the relationship between maternal SDB events and fetal heart rate (FHR) and fetal heart rate variability (FHRV).

Methods

Obese (BMI≥30kg/m2) non-smoking women carrying singleton fetuses underwent overnight polysomnography (34-37 weeks gestational age), with simultaneous fetal heart rate monitoring. Standard methods were used to score sleep, SDB events (apneas/hypopneas) and to analyze fetal heart rate parameters. Using linear mixed effect models, we examined changes in mean FHR and FHR variability (expressed by FHR SD) between the 10-second period immediately before individual SDB events, during events to the end of the associated oxygen desaturation period, and the 10-second period immediately following the SDB event.

Results

Valid PSG and FHR data were obtained from 85 third trimester maternal-fetal dyads. Across all participants, there were 2779 maternal SDB events (apneas or hypopneas). Mean AHI for individual subjects was 9.04 (SD 13.75). 39 women had OSA (AHI≥5), which was mostly mild. Mean FHR did not change significantly during and after episodes of SDB episodes compared to pre-event FHR, and did not change afterwards compared to during events, in unadjusted or adjusted (sleep stage, apnea type, degree of desaturation, age) analyses. In unadjusted analyses, FHRV significantly increased during SDB episodes compared to pre-SDB FHRV. After SDB events, FHRV was significantly lower than during SDB events. In fully adjusted models, these findings remained highly significant. FHRV was not significantly different after SDB events compared to pre-SDB event FHRV in unadjusted or adjusted models.

Conclusion

We observed consistent changes in FHR variability during and after maternal SDB events. Mean FHRV significantly increased during maternal SDB episodes compared to baseline FHRV, and decreased after SDB episodes. In contrast, mean FHR did not change significantly before, during and after SDB episodes. These data demonstrate that the fetus reacts to maternal SDB events, and raise questions about persistent effects of maternal SDB on the developing fetus.

Support

NIH HD079411

Prolongation of corneal allograft survival using cyclosporine in a polylactide-co-glycolide polymer

PURPOSE

To test for prolongation of corneal transplant survival with cyclosporine in a polymer placed in the anterior chamber of corneal allograft recipients.

METHODS

Wistar inbred rats with vascularized corneas were recipients of corneal allografts from Sprague-Dawley donor rats. Grafted rats were randomized into six groups: untreated control animals, cyclosporine-polymer anterior chamber recipients, cyclosporine-polymer subconjunctival recipients, cyclosporine-olive oil drop recipients, polymer-only anterior chamber recipients, and autografted Wistar rats. Grafts were examined by slit lamp every 3 days and the clinical condition scored. The cyclosporine concentration in the aqueous humor was assayed at 1, 2, and 4 weeks. At 2 and 4 weeks after transplantation, the eyes were collected for histopathologic evaluation of the grafts.

RESULTS

The median survival time of untreated corneal allografts was 8.2 +/- 1.48 days for grafts treated with topical cyclosporine, 8.5 +/- 1.50 days for polymer-only anterior chamber implants, 10.6 +/- 1.90 days for 1% cyclosporine drops, 11.4 +/- 2.50 days for grafts given subconjunctival cyclosporine-polymer, 17 +/- 3.05 days for grafts given cyclosporine-polymer implants in the anterior chamber, and more than 3 months in autografted rats. There was a statistically significant difference ( p < 0.05) between the survival time of the allografts in the animals treated with the cyclosporine-polymer in the anterior chamber compared with the other groups of graft recipients. Significantly higher concentrations of cyclosporine were found in the eyes given an anterior chamber implant of cyclosporine-polymer than in the other treatment groups or the untreated rats. The cyclosporine-polymer implants placed in the anterior chamber induced a transient inflammatory response in transplanted eyes.

CONCLUSIONS

Cyclosporine-polymer placed in the anterior chamber significantly prolongs corneal allograft survival in a high-risk corneal graft rejection. This intraocular delivery system may be a valuable adjunct for the suppression of immune graft rejection in high-risk recipients of corneal transplants.

Synthesis and degradation of a tri-component copolymer derived from glycolide, L-lactide, and epsilon-caprolactone

A series of tri-component copolymers was synthesized by ring opening copolymerization of cyclic lactones, i.e. glycolide, L-lactide, and caprolactone, using stannous octoate as a catalyst. Various techniques, including FT-IR, 1H NMR, DSC, X-ray diffraction, tensile strength, and contact angle measurements, were used to elucidate structural characteristics, thermal behavior, mechanical properties, and hydrophilicity of the resulting copolymers. Data showed that the properties of these copolymers could be modulated by adjusting the composition of the copolymers. The DSC and X-ray analysis demonstrated amorphous structures for most of the PGLC copolyesters. The degradation behavior of these PGLC copolymers had been studied in vitro, i.e. in 0.10 M pH 7.4 phosphate buffer solution (PBS). The degradation was monitored by intrinsic viscosity and weight loss measurements. SEM and GPC were also used to monitor the morphology and molecular weight change during degradation. The PGLC copolymers were shown to have variable degradation rates, and most of them could disappear within a few months due to their amorphous structure and low glass transition temperature.

A method for the preparation of polymeric nanocapsules without stabilizer

In this communication poly(L-lactide) (PLLA) nanocapsules containing bovine serum albumin (BSA) were prepared by means of a modified W/O/W double emulsion technology. A mixture of glycerin and water was used instead of the traditional stabilizer system in the preparation of polymeric nanocapsules. The preliminary results showed that the high viscosity of the mixture and the hydroxyl group of the glycerin were helpful to the formation of the nanocapsules. The prepared nanocapsules had a similar spherical form. By comparison of different polymers of poly(L-lactide) and polycaprolactone-poly(ethylene oxide) block copolymer (PCE), it was found that the entrapment efficiency of the BSA was strongly dependent on the hydrophilicity of the polymer. A lower entrapment efficiency of BSA and nanocapsules with smaller size were obtained when the relative hydrophilic PCE polymer was used as the entrapping material.

Synthesis and characterization of polycaprolactone/poly(ethylene oxide)/polylactide tri-componet copolymers

Polycaprolactone/poly(ethylene oxide)/polylactide tri-component copolymers (PCEL) with different compositions were synthesized by copolymerization of epsilon-caprolactone and L-lactide in the presence of poly(ethylene glycol) using stannous octoate as a catalyst. The copolymers were purified and characterized by various analytical techniques such as GPC, FT-IR, 1H NMR, 13C NMR, DSC, and X-ray diffractometry. It was evidenced that these copolymers were pure tri-component compounds which exhibited partially random chain structures, and possessed good mechanical properties and variable biodegradability.