Application of a feedforward control-based intervention for preventing hypothermia in trauma patients in a pre-hospital emergency setting.

OBJECTIVE: To investigate the efficacy of a feedforward control-based intervention strategy for preventing hypothermia among trauma patients during pre-hospital emergency care. METHODS: We conducted a retrospective analysis comparing trauma patients treated before and after implementing the intervention, with 40 cases in each group. All patients received emergency care from the Fuzhou Emergency Center on the scene. Multivariate analysis was used to explore the risk factors for hypothermia. The effective rate, incidence of adverse reactions, quality of body temperature management, medical staff's knowledge, attitudes, and behaviors regarding mild hypothermia prevention, coagulation function, treatment time at various stages, prognosis score, and treatment situation were compared between the two groups. RESULTS: The adverse reactions, intervention methods, and degree of cognitive improvement were influencing factors for hypothermia. The effective rate (92.50%) in the feedforward control group was higher than that in the non-feedforward control group (65.00%), with a lower incidence of adverse reactions (2.50%). The temperature management quality score of the feedforward control group (6.23±0.62) was higher. The feedforward control group achieved a higher quality score for temperature management (6.23±0.62) and exhibited a greater understanding of hypothermia prevention among trauma patients (P<0.05). Compared to the non-feedforward control group, the feedforward control group showed improved coagulation function, better performance in treatment time at each node, and higher prognosis scores. CONCLUSION: The intervention model based on feedforward control can effectively improve the standard of pre-hospital emergency care and prevent the incidence of hypothermia in trauma patients.

A comparative study on membrane fouling alleviation mechanisms by using nanoscale Fe3O4 and poly dimethyldiallylammonium chloride.

Membrane bioreactor (MBR) has become a promising technology for wastewater treatment. However, membrane fouling frequently occurred which greatly increased operational expense. Two different membrane fouling alleviation mechanisms were explored in this study. Addition of poly dimethyldiallylammonium chloride (PDMDAAC) facilitated formation of flocs-flocs aggregates, which were more adaptable to the changing environment, resulting in less soluble microbial products (SMP) secretion. However, PDMDAAC lose activity gradually, and had a less sustainable effect on membrane fouling alleviation. Nanoscale Fe3O4 was applied to alleviate membrane fouling, and membrane sustainable filtration cycle extended 2-fold compared to the control group. Results showed that dehydrogenase activity in the reactor with optimal addition of nanoscale Fe3O4 increased 2.86 ± 0.11 times compared to control group. SMP (especially tryptophan protein-like substances) decreased to 9.79 ± 1.34 mg L-1 with the addition of nanoscale Fe3O4, which was lower than that in the control group (15.31 ± 0.53 mg L-1). It's speculated that nanoscale Fe3O4 performed as conductive material, which intensified interspecies electron transfer. The sludge dehydrogenase activity was then enhanced, which facilitated the utilization and microbial degradation of SMP, suppressing membrane fouling consequently.

Impact of poly dimethyldiallylammonium chloride on membrane fouling mitigation in a membrane bioreactor.

Poly dimethyldiallylammonium chloride (PDMDAAC) was applied in a membrane bioreactor (MBR) to study its effects on mitigation of MBR membrane fouling. Floc size, zeta potential, soluble microbial substances (SMP) and extracellular polymeric substances (EPS) secretion were studied with respect to PDMMAAC-dosing operations. Results demonstrated that a sustainable filtration cycle extended 3.3 times with the optimal PDMDAAC dosage of 90 mg L-1. The addition of PDMDAAC could increase zeta potential of sludge floc, which led to the decrease in repulsive electrostatic interactions between flocs, as well as the facilitation of flocs-to-flocs aggregation. With the optimal dosage of PDMDAAC, the mean size of sludge was 3.23 ± 0.55 times higher than the control group, resulting in higher impact resistance and better adaptive capacity to the changing environment, which led to less SMP secretion. Moreover, a high contaminants removal rate was achieved in the reactor that was dosed with PDMDAAC. The average effluent concentrations of chemical oxygen demand and total nitrogen were less than 45.6 ± 2.85 and 5.23 ± 0.61 mg L-1, respectively, and the corresponding removal rates were 93.1 ± 5.81% and 89.1 ± 9.61%.

Coastal surface sediment quality assessment in Leizhou Peninsula (South China Sea) based on SEM-AVS analysis.

Surface sediments from the coastal area of the Leizhou Peninsula in the South China Sea were collected and analyzed and the potential ecological risks in the area were assessed based on acid-volatile sulfide (AVS) model. The AVS levels are between 0.109 and 55.6 µmol g(-1), with the average at 4.45 µmol g(-1). The high AVS-concentration zones include the aquaculture areas of Liusha Bay and the densely populated areas of Zhanjiang Bay. The simultaneously extracted metals (SEM) range from 0.026 µmol g(-1) to 8.61 µmol g(-1), with the average at 0.843 µmol g(-1). Most of high SEM-concentration stations were located in ports or aquaculture zones. Most of the coastal surface sediments of the Leizhou Peninsula (90%) had no adverse biological effects according to the criterion proposed by USEPA (2005); while adverse effects were uncertain in some stations (8%); even in 2 stations (2%) adverse biological effects may be expected.

A field study of the relationship between sulfide-bound metals and bioaccumulation by Limnodrilus sp. in a heavily polluted river.

Acid volatile sulfide (AVS) has been regarded as an important factor controlling metal bioavailability in anoxic sediments, but its effect on metal accumulation under natural conditions is poorly understood. Here, a field study of the influence of AVS on metal accumulation by Limnodrilus sp. in a heavily polluted river is provided. Most of the study area was subject to anaerobic and strongly reducing conditions, and the concentration of trace metals in surface sediments was high, as were the concentration of AVS and simultaneously extracted metals (SEM; average AVS = 20.3 µmol g(-1), average ∑SEM5 = 9.42 µmol g(-1); ∑SEM5 refers to the sum of SEMCd, SEMCu, SEMPb, SEMNi, and SEMZn). Only a few species and small quantities of benthic invertebrates were found, and Limnodrilus sp. was dominant. There was no correlation between trace metal accumulation and (SEM-AVS), and in stations where (SEM-AVS) <0, the absolute value of bioaccumulation was high (average ∑BIO5 = 4.07 µmol g(-1); ∑BIO5 refers to the sum of BIOCd, BIOCu, BIOPb, BIONi, and BIOZn), indicating that there was no relationship between (SEM-AVS) and metal accumulation in Limnodrilus sp. This was likely because Limnodrilus sp. ingest sediment particles as their main food source, so pore water metals play a minor role in their bioaccumulation (BIO) of materials. However, ∑BIO5 was significantly correlated with ∑SEM5 (r = 0.795, p < 0.01), revealing that the large number of sulfide-bound metals (SEM) in sediments may play an important role in metal accumulation in Limnodrilus sp., which can assimilate sulfide-associated metals by the help of the digestive fluids in the digestive systems.

Ecological risks assessment and pollution source identification of trace elements in contaminated sediments from the Pearl River Delta, China.

Sediments from 14 stations in the Foshan Waterway, a river crossing the industrial district of Guangdong Province, South China, were sampled and subsequently analyzed. The 14 stations were selected for the pollution discharging features of the river, such as the hydrology, the distribution of pollution sources, and the locations of wastewater outlets. The ecological risks were assessed, and the pollution sources were identified to provide valuable information for environmental impact assessment and pollution control. The spatial variability was high and the range were (in milligrams per kilogram dry weight): Pb, 46.0~382.8; Cu, 33.7~ 482.3; Zn, 62.2~1,568.7; Ni, 28.5~130.7; Cr, 34.7~1,656.1; Cd, 0.50~8.53; Hg, 0.02~8.27; and As, 5.77~66.09. The evaluation results of enrichment factor and potential ecological risk index indicate that the metal pollution in the surface and bottom sediments were severely polluted and could pose serious threat to the ecosystem in most stations. Although the hazard levels of the trace element differed among the stations, Hg was the most serious pollutant in all stations. The results of principal component analysis (PCA) show that the discharge of industrial wastewater is the most important polluting factor whereas domestic sewage, which contains a large amount of organic substances, accelerates metal deposition. And potential pollution sources were identified by the way of integrating the analysis results of PCA and data gained from the local government. Therefore, the conclusion is drawn that Foshan Waterway is seriously polluted with trace elements, both in the surface sediment (0 to 20 cm) and the bottom sediments (21 to 50 cm) are contaminated.

[AVS concentrations in Xinan Creek and the influencing factors].

Sediment and overlying water samples were collected at 10 sampling stations at Xinan Creek, a tidal river in Pearl River Delta, and analyzed for physical and chemical characteristics as well as microbial incicators, in order to reveal the main factors dominating the spatial distribution of acid volatile sulfide (AVS). The effects of Eh, SRB OC and TS on the spatial distribution of AVS were investigated and the impact of AVS on the toxicity of heavy metals in the studied area was evaluated. The results showed that the range of AVS was 0.207-41.453 micromol x g(-1), with an average of 6.684 micromol x g(-1), which is relatively high compared to the results in other studies. The AVS value of the surface layer was higher than the bottom layer in 5 stations. The AVS values in both the surface layer and the bottom layer were highly variable, the coefficients of variation being 93.61% and 153.09% , respectively. The analytical results revealed that TS was the factor with the greatest impact on the spatial distribution of AVS, and the order was TS > OC > Eh > SRB. Potential ecological risk of heavy metals existed in 60% of the smpling stations based on the value of Sigma (SEM5-AVS), however, with the criterion of [Sigma(SEM5-AVS)]/foc, none of them had inacceptable ecological risk. Furthermore, in terms of single species of heavy metals, there was certain risk of toxic effect for all the five heavy metals (Cd, Ni, Cu, Zn and Pb). The above mentioned results will provide valuable data for the in-depth study of the formation mechanism of AVS and helpful reference for environmental impact assessment and scientific rehabilitation of heavy metals in polluted rivers.

Why can water cages adsorb aqueous methane? A potential of mean force calculation on hydrate nucleation mechanisms.

By performing constrained molecular dynamics simulations in the methane-water system, we successfully calculated the potential of mean force (PMF) between a dodecahedral water cage (DWC) and dissolved methane for the first time. As a function of the distance between DWC and methane, this is characterized by a deep well at approximately 6.2 A and a shallow well at approximately 10.2 A, separated by a potential barrier at approximately 8.8 A. We investigated how the guest molecule, cage rigidity and the cage orientation affected the PMF. The most important finding is that the DWC itself strongly adsorbs methane and the adsorption interaction is independent of the guests. Moreover, the activation energy of the DWC adsorbing methane is comparable to that of hydrogen bonds, despite differing by a factor of approximately 10% when considering different water-methane interaction potentials. We explain that the cage-methane adsorption interaction is a special case of the hydrophobic interaction between methane molecules. The strong net attraction in the DWC shell with radii between 6.2 and 8.8 A may act as the inherent driving force that controls hydrate formation. A cage adsorption hypothesis for hydrate nucleation is thus proposed and discussed.

Can the dodecahedral water cluster naturally form in methane aqueous solutions? A molecular dynamics study on the hydrate nucleation mechanisms.

By performing a large scale of molecular dynamics simulations, we analyze 60 x 10(6) hydration shells of methane to examine whether the dodecahedral water cluster (DWC) can naturally form in methane aqueous solutions--a fundamental question relevant to the nucleation mechanisms of methane hydrate. The analyzing method is based on identifying the incomplete cages (ICs) from the hydration shells and quantifying their cagelike degrees (zetaC=0-1). Here, the zetaC is calculated according to the H-bond topological network of IC and reflects how the IC resembles the complete polyhedral cage. In this study, we obtain the zetaC distributions of ICs in methane solutions and find the occurrence probabilities of ICs reduce with zetaC very rapidly. The ICs with zetaC>or=0.65 are studied, which can be regarded as the acceptable cagelike structures in appearance. Both increasing the methane concentration and lowering the temperature can increase their occurrence probabilities through slowing down the water molecules. Their shapes, cage-maker numbers, and average radii are also discussed. About 13-14 of these ICs are face saturated, meaning that every edges are shared by two faces. The face-saturated ICs have the potential to act as precursors of hydrate nucleus because they can prevent the encaged methane from directly contacting other dissolved methane when an event of methane aggregation occurs. The complete cages, i.e., the ICs with zetaC=1, form only in the solutions with high methane concentration, and their occurrence probabilities are about 10(-6). Most of their shapes are different from the known hydrate cages, but we indeed observe a standard 5(12)6(2) hydrate cage. We do not find the expected DWC, and its occurrence probability is estimated to be far less than 10(-7). Additionally, the IC analysis proposed in this work is also very useful in other studies not only on the formation, dissociation, and structural transition of hydrates but also on the hydrophobic hydration of apolar solutes.