Head Space Research Articles

Comparison of head space solid phase micro extraction with conventional and comprehensive gas chromatography mass spectrometry for volatile profiling of Irish whiskey

Whiskey is a traditional distilled product produced on the island of Ireland that is currently experiencing a major expansion in export volume. Different styles of Irish whiskey exist, however only some very limited published information exists on the volatile congener profile of the different styles of Irish whiskey. Such information is potentially indispensable from a quality, flavour and authenticity perspective. As gas chromatography is the established analytical method of choice to identify volatile congeners, this study compared headspace-solid phase microextraction (HS-SPME) using conventional gas chromatography single quadrupole mass spectrometry, to HS-SPME and HS-SPME-Arrow using comprehensive two-dimensional gas chromatography (GC×GC) modulated using reverse flow in tandem with time-of-flight mass spectrometry (TOFMS) detection. Six representative Irish whiskey samples were evaluated consisting of new make spirit and mature whiskies representing Single Malts, Pot Stills and Blends. The number of volatile congeners identified in these samples by HS-SPME/HS-SPME Arrow GC×GC-TOFMS was approximately twice that detected by conventional HS-SPME GCMS. In total 145 unique individual volatile congeners, excluding ethanol were identified, with the majority consisting of esters, but also benzenes, alcohols, aldehydes, terpenoids, furans, ketones, alkanes, alkenes, norisoprenoids, acetals, acids, lactones and phenols. The use of HS-SPME Arrow GC×GC-TOFMS significantly enhances the number of volatile congeners that can be identified and therefore provides much more information that can convey insights into product quality, consistency, flavour and also for authentication purposes.

Qualitative and Untargeted Volatilome Fingerprinting of Aspergillus sp. and Bulbithecium sp. by HS-SPME-GCMS and Functional Interactions.

Research on fungal volatile organic compounds (VOCs) has increased worldwide in the last 10 years, but marine fungal volatilomes remain underexplored. Similarly, the hormone-signaling pathways, agronomic significance, and biocontrol potential of VOCs in plant-associated fungi make the area of research extremely promising. In the current investigation, VOCs of the isolates-Aspergillus sp. GSBT S13 and GSBT S14 from marine sediments, and Bulbithecium sp. GSBT E3 from Eucalyptus foliage were extracted using Head Space solid phase microextraction, followed by gas chromatography-mass spectrometry, identification, statistical analyses, and prediction of functions by KEGG COMPOUND and STITCH 5.0 databases. The significance of this research is fingerprinting VOCs of the isolates from distinct origins, identification of compounds using three libraries (NIST02, NIST14, and W9N11), and using bioinformatic tools to perform functional analysis. The most important findings include the identification of previously unreported compounds in fungi-1-methoxy naphthalene, diethyl phthalate, pentadecane, pristane, and nonanal; the prediction of the involvement of small molecules in the degradation of aromatic compound pathways and activation, inhibition, binding, and catalysis of metabolites with predicted protein partners. This study has ample opportunity to validate the findings and understand the mechanism or mode of action, the interspecies interactions, and the role of the metabolites in geochemical cycles.

Investigating the emission of volatile organic compound from Cinnamomum camphora

Woodwork has functions as the versatile and sustainable furniture material to decorate buildings in our low-carbon society, while commonly giving significant risks of releasing volatile organic compound (VOC). Thus, how to accurately identify and quantify the VOC of woodwork raw materials is critical. Herein, we designed an easy-to-handle, processable, time-saving strategy of coupling headspace (HS) and gas chromatography (GC) to effectively and precisely investigate the emission behavior of VOC of Cinnamomum camphora (C. camphora). The effects of operation parameters of HS-GC on the VOC emission are analyzed in detail, where the optimize treatment conditions are 140 °C of equilibrium temperature, 25 h of equilibrium time, and 20–40 mesh of particle size. In addition, camphor and eucalyptol are the main chemical components of VOC, which shows the high content, more than 50 % of harvesting VOC. Moreover, a semi-empirical model for VOC emission of C. camphora is established, in which the predicted VOC emission demonstrates a strongly linear relationship with the experimental results (R2 > 0.99). This study enables the comprehensive understanding of VOC emission of raw materials of woodwork, beyond C. camphora, and provides references to effectively reduce VOC in sustainably building and construction.

Profiling the volatile compounds of Peganum harmala L. Based on multiple sample preparation coupled with gas chromatography-mass spectrometry analysis and explored its antidepressants-like activity

Peganum harmala L., a traditional medicinal plant in China, is renowned for its significant alkaloid content in seeds and roots exhibiting a wide range of pharmacological activities, including antidepressant, antiseptic, and antiviral. However, the volatile composition of the herb remained unclear. Apart from that, the extraction of volatile compounds through essential oil presents challenges due to the low yield and the degradation of volatile active compounds at high temperatures. This study used multiple sample preparation methods including headspace (HS), needle trap device (NTD), and liquid–liquid extraction (LLE) coupled with gas chromatography-mass spectrometry (GC–MS) to analyze the volatile compounds from the areal part of P. harmala L.. A total of 93 compounds were identified with NTD facilitating the first detection of harmine among the volatile organic compounds. Through network pharmacology and protein interaction analysis, the compounds’ potential therapeutic targets of the compounds were explored, and 23 key targets were obtained (AKT1, ALB, PTGS2, MAOA, etc). KEGG pathway enrichment analysis indicated significant involvement in neuroactive ligand-receptor interactions and serotonergic synapses. The results enhanced the understanding of P. harmala’s pharmacological mechanisms and supported its ethnopharmacological use.

Halal aspect and nutritional potential of telang (Clitoria ternatea L.) flower kombucha

Abstract Public awareness of halal aspects is increasing, especially for foods. Indonesian Ulema Council (MUI) states that fermented drinks are halal if they contain alcohol below 0.5%. Several compounds are produced during the fermentation process in kombucha, including the compound ethanol (alcohol). This research aims to analyze the alcohol content and nutritional content of telang (Clitoria ternatea L.) flower kombucha drinks to fulfil halal aspects and nutritional potential. This research is an experimental study using a Completely Randomized Design (CRD) with one factor, namely storage time at five observation points (0 weeks, 1 week, 2 weeks, 3 weeks, and 4 weeks). The alcohol content was analyzed using a method using Gas Chromatography with Flame Ionization Detection- Head Space (GC-FID). Nutrient content analysis consists of analysis of water, ash, energy, energy from fat and protein content, and carbohydrate analysis carried out by difference. Total sugar content was analyzed using High-Performance Liquid Chromatography (HPLC). The alcohol content increases during the storage period. Alcohol content is in the range of 0.15-0.17%. This content meets halal aspects with a content of <0.5% following MUI regulations. Statistical analysis using ANOVA showed that storage had no significant effect on alcohol content (p>0.05). Telang flower kombucha contains 117.46 calories of energy, 29.37 grams of carbohydrates, 0.02 grams of fat, 0.04 grams of protein, and 16 grams of sugar per 100 ml.

GC/MS analyses, FTIR and quantum mechanics calculations of poly Vinyl Alcohol in neutral and irradiated state

The products obtained from a poly vinyl alcohol (PVA) at non-irradiated and irradiated state were identified. The analyses were carried out using Head Space (HS) – Gas Chromatography – Mass Spectrometry (HS-GC/MS) instruments. On the other hand, FTIR spectroscopy has been done to explain the functional groups present. Also, the quantum chemical calculations using DFT (Density Function Theory) method were used to confirm the fragmentation process of the GC/MS chromatogram and the mass spectra of non-irradiated and irradiated PVA products. The HS-GC/MS analysis exhibited that fourth according to namely: 2-Butene, 2-methyl- (MW = 70), Cyclohexene (MW = 82), Benzocyclopropene (MW = 90), and Benzene, 1,2,4-trimethyl (MW = 120) have been detected and identified according to its GC/MS chromatogram outcomes. The mass spectrum of each component has been recorded and confirms the molecular ion peak. The obtained results show that the peaks begin to develop as the irradiation dose increases, and that this proportion rises as the gamma dose increases. Furthermore, every component of the fragment appears in the GC/MS chromatogram at a higher relative intensity of Selected ion motoring (SIM) as gamma dosages increase for each molecule. An induced change in the band intensities has been observed in FTIR spectra, which indicates cleavage in the CH bond after irradiation. In both cases, it was found a significant difference between the fragmentation products of the PVA at non-irradiated and irradiated state. Density functional theory (DFT) provides theoretical confirmation of this for both irradiated and non-irradiated PVA states.

Evaluation of three granular activated carbon filters for the treatment of collections foul air entering a water resource recovery facility.

The treatment of raw foul air that could escape to the atmosphere from the head space of the incoming wastewater sewer lines into a Southern California Water Resource Recovery Facility was evaluated by using a 1/20th scale pilot unit consisting of three different granular activated carbon filter technologies, operating side by side, under similar operating conditions, each having an average 3.8-s contact time. The three activated carbon filters contained each 0.07 m3 of coconut, coal, and coconut mixed with permanganate media. The foul air entering the granular activated carbon filters contained 82% to 83% relative humidity. No moisture removal mechanism was used prior to treatment. The removal of six different odor characters from eight chemical odorants present in the foul air were assessed. These were rotten egg (hydrogen sulfide), rotten vegetables (methyl mercaptan), canned corn (dimethyl sulfide), rotten garlic (dimethyl disulfide), earthy/musty (2-methyl isoborneol and 2-isopropyl 3-methoxy pyrazine), and fecal (skatole and indole). This is the first time a study evaluates the removal of specific odors by simultaneously employing sensory analyses using the odor profile method, which defines the different odor characters and intensities, together with chemical analyses of the odorants causing these odors. The results show that the three granular activated carbon filters, before hydrogen sulfide breakthrough, provided significant improvement in odor intensity and odorant removal. Breakthrough was reached after 57 days for the coconut mixed with permanganate, 107 days for the coconut, and 129 days for the coal granular activated carbon filter. Breakthrough (the critical saturation point of the activated carbon media) was considered reached when the hydrogen sulfide percentage removal diminished to 90% and continued downward. The coconut mixed with permanganate granular activated carbon filter provided the best treatment among the media tested, achieving very good reduction of odorants, as measured by chemical analyses, and reasonable removal of odor intensities, as measured by the odor profile method. The coconut mixed with permanganate granular activated carbon is recommended for short-term odor control systems at sewer networks or emergency plant maintenance situations given its shorter time to breakthrough compared with the other granular activated carbons. The coal and coconut granular activated carbon filters are generally used as the last stage of an odor treatment system. Because of the observed poor to average performance in removing odorants other than hydrogen sulfide, the treatment stage(s) prior to the use of these granulated activated carbons should provide a good methyl mercaptan removal of at least 90% in order to avoid the formation of dimethyl disulfide, which, in the presence of moisture in the carbon filter, emit the characteristic rotten garlic odor. The differences observed between the performances based on odorant removal by chemical analysis compared with those based on sensorial analyses by the odor profile method indicate that both analyses are required to understand more fully the odor dynamics. PRACTITIONER POINTS: Three virgin granulated activated carbon media were evaluated in a field pilot unit using raw collections foul air. Coal, coconut, and coconut mixed with permanganate were tested until breakthrough. Samples were analyzed both chemically (odorants) and sensorially (odors). Coconut mixed with permanganate proved to be the media that better reduced odorants and odors.

Risk factors for life-threatening complications of head and neck space infections: A systematic review and meta-analysis

ObjectiveThe present systematic review was performed to identify risk factors associated with life-threatening complications of head and neck space infections (LCHNSI) within the included studies and assess the magnitude of their impact on patients. MethodsWe systematically searched PubMed, Web of Science, EmBase, Scopus and CNKI for articles that reported risk factors associated with life-threatening complications of head and neck space infections from inception to 14 December 2023. Only factors reported in at least three papers were considered in the meta-analysis. Pooled odds ratio (OR) and 95 % confidence interval (CI) were calculated using fixed effects model and random effects model. The between-study heterogeneity of effect size was quantified using the Q statistic and I2. In addition, subgroup analysis stratified by study characteristics and sensitivity analysis were performed to explore the potential sources of heterogeneity and the stability of the results. ResultsThe review included a total of 29 studies. The results revealed that the risk factors which associated with LCHNSI were included diabetes mellitus (OR = 3.31, 95 % CI: 2.49–4.40), total leukocyte count(≥15 × 109/L) (OR = 1.21, 95 %CI: 1.04–1.42), multiple space involvement (OR = 4.32, 95 %CI: 3.47–5.38), combined systemic diseases (OR = 9.94, 95 %CI: 6.30–15.67), advanced age(≥60) (OR = 3.90, 95 %CI: 2.80–5.44), dyspnoea (OR = 23.39, 95 %CI: 12.41–44.10), high temperature(≥39°C) (OR = 3.23, 95 %CI: 2.02–5.17), retropharyngeal space involvement (OR = 3.62, 95 %CI: 2.06–6.35), parapharyngeal space involvement (OR = 4.62, 95 %CI: 2.27–9.42). ConclusionsAccording to the current analysis, diabetes mellitus, total leukocyte count(≥15 × 109/L), combined systemic diseases, multiple space involvement, advanced age(≥60), dyspnoea, high temperature (≥39 °C), retropharyngeal space involvement, parapharyngeal space involvement were the risk factors for LCHNSI. To mitigate the incidence of LCHNSI, clinical staff should carefully manage these risk factors, ensure prompt diagnosis, and implement timely preventive measures.

Online sequential analysis of volatile and semivolatile organic compounds in water matrices by double robotic sample preparations and dual-channel mono and comprehensive two-dimensional gas chromatography coupled with time-of-flight mass spectrometry system

The monitoring of organic compounds in aquatic matrices poses challenges due to its complexity and time-intensive nature. To address these challenges, we introduce a novel approach utilizing a dual-channel mono (1D) and comprehensive two-dimensional (2D) gas chromatography coupled with time-of-flight mass spectrometry (GC × GC–TOFMS) system, integrated with a robotic pretreatment platform, for online monitoring of both volatile organic compounds (VOCs) and semivolatile organic compounds (SVOCs) in water matrices. Employing the robotic platform, we establish a suite of online liquid–liquid extraction (LLE) pretreatment processes for water samples, marking the first instance of such procedures. Leveraging the automatic headspace (HS) module, dual robotic preparations of HS and LLE are sequentially executed to extract VOCs and SVOCs from water matrices. The GC × GC–TOFMS system is distinguished by its dual-channel analytical column configuration, facilitating sequential analysis of VOCs in GC–TOFMS mode and SVOCs in GC × GC–TOFMS mode. Quantitative detection of 55 target VOCs and 104 SVOCs is achieved in a water sample using the instrument system. Our method demonstrates excellent correlation coefficients ranging from 0.990 to 1.000, method detection limits ranging from 0.08 to 4.78 μg L–1, relative standard deviations below 19.3 %, and recovery rates ranging from 50.0 % to 124.0 %. To validate the online monitoring capabilities of our system, we assess target SVOCs at three different concentration levels over a 3-day period. Most compounds exhibit recovery rates ranging from 70.0 % to 130.0 %. Furthermore, we apply our method to analyze a real water sample, successfully identifying over 100 target and nontarget VOCs/SVOCs, including alcohols, aldehydes, ketones, acids, esters, and phenols. These results highlight the efficacy of the proposed analysis system, capable of conducting two distinct analyses in automatic sequence, thereby enhancing the efficiency and accuracy of organic compound analysis in water matrices.

Streptomyces strains inhibit the growth of Fusarium kuroshium and Fusarium solani and promote the growth of Arabidopsis thaliana

ABSTRACT Three Streptomyces strains (S. lactacystinicus CIAD-IA7, S. cellostaticus CIAD-IA32 and S. lunaelactis CIAD-IA104) were selected among 21 strains of this genus according to their antifungal activity against Fusarium solani (model fungus) and then, used to evaluate their activity against Fusarium kuroshium cultures (target fungus). The in vitro plant growth promoting properties (PGP) of these strains were also determined in A. thaliana seedlings. The three strains suppressed 95.4-97.9% the mycelial growth of F. solani in dual cultures. The exposure of the pathogen to VOCs produced axenically by the Streptomyces strains reduced its growth by 84.3–92.5%, confirming the antifungal properties of VOCs from Streptomyces. The analysis of the head space from axenic cultures of the selected Streptomyces strains revealed the groups of VOCs, but ethylbenzene, o-xylene, 2-pentylfuran, cyclohexene, and 1-methyl-4-(1-methylethenyl)-, (S)- were the most abundant. Further studies with seven pure VOCs that had been identified in selected Streptomyces strains confirmed the antifungal activity of VOCs from Streptomyces against F. solani, with trans-2-hexenal and eucalyptol inhibiting >50 and 100%, respectively, the growth of the pathogen. The inhibition of F. kuroshium by the selected Streptomyces ranged from 51.2 to 64.5% in dual-cultures and from 58.4 to 66.5% by VOCs. Streptomyces strains also produced indole-3-acetic acid and siderophores. VOCs from Streptomyces cultures also favoured biomass accumulation in A. thaliana seedlings. The most significant increases in biomass were observed in root length, plant fresh weight, and root fresh weight. The selected Streptomyces strains might be candidates to be used as biofungicides and biofertilisers.

Effect of nitrate supplementation on diurnal emission of enteric methane and nitrous oxide

The objective of this study was to investigate the effect of nitrate supplementation on diurnal enteric methane (CH4) and nitrous oxide (N2O) emissions in dairy cows. Four Danish Holstein dairy cows fitted with ruminal cannulas were used in a 2 × 2 crossover design with 2 periods of 14 d duration. Cows were fed ad libitum with 2 experimental diets based on either urea or nitrate (8.6 g NO3−/kgofDM) supplementation. Samples of ruminal fluid, blood, and rumen headspace gas samples were collected. Gas exchange was measured in respiration chambers during a 96-h period. N2O emission was calculated from the ratio between CH4 and N2O in the rumen head space and the measured CH4 emission. Nitrate supplementation resulted in a lower daily CH4 production (g/d), CH4 yield (g/kg of DMI), a lower CH4 per kg of FPCM, a tendency of lower CH4 intensity (g/kg ECM), and higher daily hydrogen (H2) production, H2 yield, and daily N2O production compared with urea supplementation. The only difference in ruminal volatile fatty acid composition was a higher valerate proportion in cows receiving nitrate compared with urea supplementation. In conclusion, nitrate compared with urea supplementation reduced CH4 production, mainly just after feeding, but also increased N2O production.

EKSPLORASI JENIS-JENIS LEBAH MADU TAK BERSENGAT DI KEPULAUAN ARU

Exelation aims to find what types of stingless honey bees are there in the Aru Islands. The research was carried out on the Aru Islands, Wamar Island (Wangel and Durdiela Village), Kobror Island (Warbola and Benana Village), and Koba Island (Mutrai and Koba Village) from March to July 2022. The method used in preciation in Vata is a descriptive method, namely identifying stingless honey bees through observation, morphological characteristics and measurements, morphometrics and describing the location of the eccomium. Research shows that stingless honey bee stings were found. In Kalman Aru there were 36 active colonies at a height of 1-241 cm, with nesting sites found namely cave cavities, stone cavities and Ulouran rates. The average morphometric character of Tetragonula capens worker stratum bees found was long. body 374-4 25mm, head width 177-1 81mm. head space 1 47-1 55mm, wing length 3.81-4-35mm, antenna length 170-173mm, while Tetragonula cobalteata which was found, body length 278-324mm, head width 1 18-132 mm, head length 109-123 mm wing length and tegula 316-3.22 mm, and antenna length 2 18-2.22 mm.

Biomarker Aroma Compounds of Monofloral Honey From Kazakhstan by Gas Chromatography–Mass Spectrometry (GC–MS) and Chemometric Analysis*

The aroma compounds of honey provide useful information to determine the geographical origin. This work focuses on the study of aroma compounds of 16 honey samples using headspace (HS)-solid-phase microextraction (SPME) gas chromatography–mass spectrometry (GC-MS) to reaffirm the geographical features of 4 monofloral honey. 7 sunflower, 3 buckwheat, 2 agrimonia, and 4 tamarix monofloral honey samples were obtained from four regions of Kazakhstan. Moreover, the GC-MS data were applied to chemometric analysis for the common aroma compounds to discriminate the monofloral honeys. In total, 76 aroma compounds were detected and 72 were identified. α-Pinene, benzaldehyde, octanal, hotrienol, limonene, cosmene, nonanol, linalool oxide, dehydro-p-cymene, β-linalool, 2-nonen-1-ol, carvacrol, lilac aldehyde A, β-citral, 2-decen-1-al, and β-damascenone were identified as common aroma compounds for all honey types. According to principal component analysis (PCA), the aroma compounds of sunflower, buckwheat, agrimonia, and tamarix honey were distinguished. Dehydro-p-cymene, β-linalool, 2-nonen-1-ol, and linalool oxide were determined as dominant compounds for agrimonia honey, while nonanol, benzaldehyde, octanol, dehydro-p-cymene and β-linalool for buckwheat, β-citral, lilac aldehyde A, 2-decen-1-al, D-limonene, β-damascenone, linalool oxide for tamarix honey, and hotrienol, cosmene, α-pinene, and carvacrol for the sunflower product. PCA revealed that the dominant compounds for each honey could be used as biomarker compounds to detect the origin of the honey and possible adulteration, such as blending and inverted sugar addition.

Increasing Incidence of Streptococcus anginosus Group Intracranial Infections Associated With Sinusitis, Otitis Media, and Mastoiditis in Children.

The Streptococcus anginosus group (SAG) pathogens have the potential to cause head and neck space infections, including intracranial abscesses. Several centers noted an increase in intracranial abscesses in children during the SARS-CoV-2 pandemic, prompting a Centers for Disease Control and Prevention health alert in May 2022. We examined the epidemiology of pediatric intracranial abscesses at a tertiary care center with a focus on SAG pre- and post-pandemic. Cases of intracranial abscesses of any microbiologic etiology admitted from January 2011 to December 2022 were identified using International Classification of Diseases 10 codes. Subjects were cross-referenced with culture results from the microbiology laboratory at Texas Children's Hospital. Cases included were those associated with either otitis media, mastoiditis or sinusitis and medical records were reviewed. A total of 157 cases were identified and 59.9% (n = 94) were caused by SAG. The incidence of all sinogenic/otogenic intracranial infections ( P = 0.002), and SAG-specific infections ( P = 0.004), increased from 2011 to 2022. SAG infection was more often associated with multiple surgeries, and these subjects were more likely to require craniotomy or craniectomy. Among sinogenic abscesses, S. intermedius was the most common pathogen, while among otogenic cases, S. pyogenes predominated. From March 2020 to Dec 2022, 9/49 cases tested positive for SARS-CoV-2 (18.4%); characteristics of infection were not significantly different among cases with and without SARS-CoV-2. Over the last decade, intracranial complications of sinusitis/otitis have been increasing, specifically those caused by SAG; this trend, however, predated the SARS-CoV-2 pandemic. SAG was associated with a greater need for surgical intervention, specifically neurosurgery. Further work is necessary to determine the cause for these rising infections.

New paradigm shifts in micropropagation of fruit crops through bioreactors - a review

within relatively shorter periods, as well as significant reductions in hyperhydricity in plants as a result of efficient gas exchange, oxygen supplementation and automation, bioreactors, specifically temporary immersion systems (TIS), are being utilized for mass multiplication of forestry and horticultural crops. In tissue culture of banana, date palm, strawberrys, papaya, citrus, grape, pineapple, apple, pear, plum, chestnut, pistachio nut, apricot, sweet cherry, and almond, a variety of TIS bioreactors were used, including RITA, Plantform, SETIS and twin glass airlifts. TIS Bioreactors need to be improved in terms of space utilization. The space utilization was found to be highest with the Plantform system (80%) and lowest in the Twin Flask system (26%). Higher head space provides better plant growth and lesser fogging on the walls of the bioreactor. Most bioreactors have not been designed to facilitate better root production in vitro. Roots get coiled and cluttered, which needs improvement in design. The provision of illumination in each tank will facilitate better morphogenesis. This paper describes the micropropagation of fruit crops using different TIS bioreactors.

Design and damping performance analysis of a multistage meandering hybrid valved magnetorheological damper

Abstract The current valved magnetorheological damper has a low space utilization of the piston head, which results in insufficient output damping force, and this paper proposed a multistage meandering hybrid valved magnetorheological damper. The three-dimensional structure of the damper is established and its mathematical model is derived. The electromagnetic field finite element analysis was used to simulate the damper structure, and a comparison was made between the results of traditional annular valve structures and those of multistage meandering hybrid valve. The damping performance of a multistage meandering hybrid valved damper was experimentally studied. The results indicate that the maximum output damping force of the multistage meandering hybrid valved structure is increased by 62.2% over the traditional annular valved structure at a current of 2.4 A and a coil turn count of 350 turns. The structure can effectively utilize the piston head space and improve the output damping force of the damper. The output damping force of the damper reaches 486.4N and the adjustable coefficient K reaches 8.6. The numerical simulation results are the same as the actual experimental results.

Numerical Simulation on Dispersion of Hydrogen Leaked in Particle Layers of Glass Beads and Soil

In order to understand the dispersion of hydrogen (H2) leaked in packed beds of nonporous/porous particles in a partially open space practically, the dispersion of H2 in the particle layers of glass beads and soil was analytically studied using a computational fluid dynamics code to be compared with the experiments and to elucidate the effects of the particle layer. The packed beds in the partially open space can be considered as a basic model for all processes of transfer, treatment, storage, and disposal of radioactive materials containing fuel debris in the decommissioning of nuclear facilities after a severe accident. The H2 flowing out from a single leak point in the particle layer of nonporous glass beads was affected by buoyancy around the leak point and diffused directly above the leak point in an elliptical shape faster than in the horizontal direction. After that, when it reached the air layer in the head space above the particle layer, the H2 spread horizontally, formed a large concentration gradient near the boundary between the particle layer and the air layer, and further diffused in the air layer until the H2 concentration became about 1/3 or less of the concentration near the surface of the particle layer. When the particle diameters were 512 μm and 1200 μm, this tendency was more pronounced when the porosity was the same and the particle diameter was smaller. The calculations largely reproduced the experimental concentration distributions. When the particle layer was porous decomposed granite soil, the diffusion behavior of H2 in the particle layer proceeded in the same manner as in the case of the glass beads. However, a large concentration gradient was formed near the boundary between the particle layer and the air layer, and then H2 diffused in the air layer until the H2 concentration became below the lower combustion limit. It was suggested through sensitivity analysis that the air permeability coefficient had a large effect on the time course of the H2 concentration distribution. Based on this information, we further simulated H2 behavior in the vessel containing the H2 leaked particle layer. By inserting multiple vent pipes without considering H2 generation distribution and particle properties in the particle layer, H2 accumulated from one pipe was discharged by buoyancy without depending on the H2 generation distribution and particle properties in the particle layer and air flowed in from the other pipe. It was suggested that such a natural ventilation process would reduce the H2 concentration in the container.

Length-controlled hydrophobic CF3-COF as a highly efficient absorbent coating for dual-mode solid-phase microextraction of sixteen polycyclic aromatic hydrocarbons in water samples

Polycyclic aromatic hydrocarbons (PAHs), a group of seriously hazardous environmental contaminants, have attracted extensive attention due to their carcinogenicity, genotoxicity, mutagenicity, and ubiquity. In this work, the excellent hydrophobic trifluoromethyl-enriched covalent organic framework (CF3-COF) was designed and synthesized as coating of solid-phase microextraction (SPME). The CF3-COF offered a high adsorption selectivity for PAHs, which could be attributed to the multiple interactions between the CF3-COF and PAHs, including hydrophobicity interaction, π-π and H bond interactions. Furthermore, headspace (HS) and direct immersion (DI) dual-mode solid-phase microextraction (HS/DI-SPME) were innovatively integrated as a dual-mode extraction by varying the length of SPME coating on stainless-steel, which could simultaneously and efficiently extract 16 PAHs with different volatile. Amazingly, the proposed strategy achieved fast adsorption for PAHs and shortened the adsorption equilibrium time to 15 min. By further integrating with gas chromatography tandem mass spectrometry (GC–MS/MS), PAHs could be detected in the range of 0.008–0.16 ng mL−1 with a quantitative limit of 0.029–0.47 ng mL−1, respectively. The recoveries of PAHs in water samples ranged from 80.84 to 117.67 %. This work indicates that the dual-mode CF3-COF-SPME is a promising candidate for the enrichment of multiple hazardous substances in complicated samples.

Improved Quantification of Geosmin and 2-Methylisoborneol in Farmed Fish Using Stable Isotope Dilution Gas Chromatography-Mass Spectrometry.

A requisite to improving the taste and odor attributes of farmed fish is the availability of accurate and practical analytical methods to quantify 2-methylisoborneol (MIB) and geosmin (GSM). Solid-phase microextraction (SPME) enables reliable measurement of nanogram per liter quantities of MIB and GSM in water. In contrast, direct headspace (HS)-SPME of biological matrices with variable proximate compositions can increase bias and uncertainty in off-flavor determinations. Analytical recovery plays a crucial role in the accurate determination of MIB and GSM in fish, and this study investigates strategies to maximize and account for this recovery factor. MIB and GSM values in off-flavor catfish and trout were measured using direct HS-SPME and distillation as sample preparation techniques. Trout samples prepared by distillation yielded 10-fold higher GSM recoveries than those from direct HS-SPME (31% versus 3%). A stable isotope dilution method (SIDM) was implemented by routinely spiking samples with known quantities of deuterium-labeled MIB and GSM, allowing for the correction of sample-to-sample recovery deviations. SIDM-determined GSM values generated recoveries of 106 and 95% for direct HS-SPME and distilled trout, respectively. Aspects of the strategies and techniques presented can be incorporated into existing analytical methods to improve the accuracy and sample throughput. Particularly, routine inclusion of SIDM in the evaluation of MIB and GSM can facilitate identification of reliable practices to control off-flavors in aquaculture.

Performance Evaluation of Balcony Designs for Mitigating Ground Level Noise

This study aims to tackle the challenge of high noise levels on balconies while preserving natural ventilation. Eight innovative balcony designs, incorporating elements like diffuser edges, undulating ceilings, Helmholtz resonators, grooves, or sound traps, were evaluated via finite element (FE) modeling. The insertion loss results showed that for many balcony designs, noise reduction in the balcony could deteriorate beyond an elevation of 8 m. However, the front jagged and full wavy ceiling designs were shown to be more robust in noise attenuation across balconies on different floors. The jagged ledge and grooved parapet designs yielded an overall 1.5 dBA lower SPL at the exterior regions, compared to other designs, which implies that the designs are less acoustically detrimental to nearby residential blocks as they tend to diffract and absorb incident noise. The jagged ledge design is more effective for lower floors while the jagged ceiling design is more effective for higher floors. A combination of the protruded jagged ledge for the lower floor and jagged balcony ceiling for the higher floor would result in the lowest noise ingress over three stories of residential units: this would be capable of achieving more than 3 dB noise reduction and would offer viable options for improving balcony noise mitigation, by providing valuable insights to architects and designers seeking practical solutions for outdoor noise reduction. Our study highlights that whereas the spectrum characteristics of acoustic absorption materials may be less tunable, and where reduced head space is traded for thicker material for greater ab-sorption and added affixation and maintenance cost, the jagged ledge and ceiling curvatures can actually be shape-tuned, say for every 3 to 4 floors up the high-rise to more effective reduce noise ingress and possibly improve the architecture façade outlook.