Effect of ultraviolet blood irradiation and oxygenation on nerve function and function of the red blood cell membrane pump in patients with acute cerebral infarction

BACKGROUND： Ultraviolet blood irradiation and oxygenation （UBIO） has obtained better clinical effect in treating acute cerebral infarction, but the mechanism underlying this effect remains unclear. OBJECTIVE： To observe the effect of UBIO on the nerve function and activities of K^＋-Na^＋-ATPase and Ca2^＋-Mg2^＋-ATPase activities on the red blood cell （RBC） membrane of patients with acute cerebral infarction. DESIGN： A randomized and controlled study.SETTING： Department of Neurology, Xiangfan Central Hospital.PARTICIPANTS： From January 2000 to December 2001, excluding those above 70 years old, 58 cases of 700 patients with acute cerebral infarction admitted in the Department of Neurology, Xiangfan Central Hospital, were recruited and divided into two groups according to the random number table： UBIO treated group （n=28）, including 17 males and 11 females, aged 40-68 years; and control group （n=30）, including 20 males and 10 females, aged 44-69 years. All the patients agreed to participate in the therapeutic program and detected items. The general informations were comparable without obvious differences between the two groups （P 〉 0.05）.METHODS： ① The patients in both groups received routine treatments, besides, those in the UBIO treated group were given UBIO treatment by using the XL-200 type therapeutic apparatus produced in Shijiazhuang, whose ultraviolet wave was set at 253.7 nm with the energy density of 0.568 J/m^2 per second, UBIO treatment started from the second day after admission, once every other day, with a single course consisting of 5-7 treatments. ② In the UBIO treated group, the venous blood was sampled before and after the first, third and the completion of the treatment course respectively, the venous blood was taken at each corresponding time point in the control group. After centrifugation of the blood at 10 000 rounds per minute, the RBC membrane was separated and then the activities of K^＋-Na^＋-ATPase and Ca2^＋-Mg2^＋-ATPase were detected by means of phosphorus determination.③ The nerve function was scored before and after treatment in both groups with European stroke scale, which included 13 items, the total score was 0-100 points, the higher the score, the better the nerve function. MAIN OUTCOME MEASURES ：①Score of European stroke scale before and after treatment in both groups.② Comparison of the activities of K^＋-Na^＋-ATPase and Ca2^＋-Mg2^＋-ATPase on RBC membrane between the two groups before treatment and after the first, third and the completion of the treatment. RESULTS： All the 58 patients with cerebral infarction were involved in the analysis of results.① The score of European stroke scale had no obvious difference between the two groups [（49.31±11.48）, （50.58±12.63）, P 〉 0.05], and it was obviously higher in the UBIO treated group than in the control group after treatment [84.66±13.75）, （77.05±11.17）, P 〈 0.05].②The activity of K^＋-Na^＋-ATPase on RBC membrane in the UBIO treated group was significantly increased after the first and third treatment as compared with before treatment [（31.56±19.25）, （27.64±15.83）, （17.67±13.83）, P 〈 0.01], it was still higher after the completion of the treatment than before treatment without obvious difference [（20.86±14.53）, P 〉 0.05]. After the first and third treatment, it was obviously higher in the UBIO treated group than in the control group [19.31±11.88）, （17.44±10.42）, P 〈 0.01]. ③ In the UBIO treated group, Ca2^＋-Mg2^＋-ATPase activity on RBC membrane significantly increased after the first treatment and remained higher than the pre-treatment level throughout the treatment [（27.49±14.72）, （17.41±4.82）, P 〈 0.01]. The activity of Ca2^＋-Mg2^＋-ATPase on RBC membrane was markedly higher in the UBIO treated group than in the control group after after the first, third and the completion of treatment respectively [（24.83±12.88）, （17.70±5.69）; （28.08±13.44）, （16.32±5.29）; （17.42±6.04）, P〈 0.05-0.01]. CONCLUSION： The effect of UBIO treatment against acute cerebral infarction may be mediated by the increased K^＋-Na^＋ ATPase and Ca2^＋-Mg2^＋-ATPase activities on RBC membrane, which enhances the RBC transformation ability so as to lower RBC aggregation and correct high blood viscosity.

Hard-carbon hybrid Li-ion/metal anode enabled by preferred mesoporous uniform lithium growth mechanism

To achieve high energy density in lithium batteries,the construction of lithium-ion/metal hybrid anodes is a promising strategy.In particular,because of the anisotropy of graphite,hybrid anode formed by graphite/Li metal has low transport kinetics and is easy to causes the growth of lithium dendrites and accumulation of dead Li,which seriously affects the cycle life of batteries and even causes safety problems.Here,by comparing graphite with two types of hard carbon,it was found that hybrid anode formed by hard carbon and lithium metal,possessing more disordered mesoporous structure and lithophilic groups,presents better performance.Results indicate that the mesoporous structure provides abundant active site and storage space for dead lithium.With the synergistic effect of this structure and lithophilic functional groups(–COOH),the reversibility of hard carbon/lithium metal hybrid anode is maintained,promoting uniform deposition of lithium metal and alleviating formation of lithium dendrites.The hybrid anode maintains a 99.5%Coulombic efficiency(CE)after 260 cycles at a specific capacity of 500 m Ah/g.This work provides new insights into the hybrid anodes formed by carbon-based materials and lithium metal with high specific energy and fast charging ability.

Proof of Aerobically Autoxidized Self-Charge Concept Based on Single Catechol-Enriched Carbon Cathode Material

The self-charging concept has drawn considerable attention due to its excellent ability to achieve environmental energy harvesting,conversion and storage without an external power supply.However,most self-charging designs assembled by multiple energy harvesting,conversion and storage materials increase the energy transfer loss;the environmental energy supply is generally limited by climate and meteorological conditions,hindering the potential application of these selfpowered devices to be available at all times.Based on aerobic autoxidation of catechol,which is similar to the electrochemical oxidation of the catechol groups on the carbon materials under an electrical charge,we proposed an air-breathing chemical self-charge concept based on the aerobic autoxidation of catechol groups on oxygen-enriched carbon materials to ortho-quinone groups.Energy harvesting,conversion and storage functions could be integrated on a single carbon material to avoid the energy transfer loss among the different materials.Moreover,the assembled Cu/oxygen-enriched carbon battery confirmed the feasibility of the air-oxidation self-charging/electrical discharging mechanism for potential applications.This air-breathing chemical self-charge concept could facilitate the exploration of high-efficiency sustainable air self-charging devices.

Compensatory recombination phenomena of neurological functions in central dysphagia patients

We speculate that cortical reactions evoked by swallowing activity may be abnormal in patients with central infarction with dysphagia. The present study aimed to detect functional imaging features of cerebral cortex in central dysphagia patients by using blood oxygen level-depen- dent functional magnetic resonance imaging techniques. The results showed that when normal controls swallowed, primary motor cortex （BA4）, insula （BA13）, premotor cortex （BA6/8）, supramarginal gyrus （BA40）, and anterior cingulate cortex （BA24/32） were activated, and that the size of the activated areas were larger in the left hemisphere compared with the right. In re- current cerebral infarction patients with central dysphagia, BA4, BA13, BA40 aild BA6/8 areas were activated, while the degree of activation in BA24/32 was decreased. Additionally, more areas were activated, including posterior cingulate cortex （BA23/31）, visual association cortex （BA18/19）, primary auditory cortex （BA41） and parahippocampal cortex （BA36）. Somatosen- sory association cortex （BA7） and left cerebellum in patients with recurrent cerebral infarction with central dysphagia were also activated. Experimental findings suggest that the cerebral cortex has obvious hemisphere lateralization in response to swallowing, and patients with recurrent cerebral infarction with central dysphagia show compensatory recombination phenomena of neurological functions. In rehabilitative treatment, using the favorite food of patients can stimu- late swallowing through visual, auditory, and other nerve conduction pathways, thus promoting compensatory recombination of the central cortex functions.

Fabrication and study of supercapacitor electrodes based on oxygen plasma functionalized carbon nanotube fibers

Dry-spun Carbon Nanotube(CNT)fibers were surface-modified by atmospheric pressure oxygen plasma functionalization using a well controlled and continuous process.The fibers were characterized by scanning electron microscopy(SEM),Raman spectroscopy,and X-ray Photoelectron Spectroscopy(XPS).It was found from the conducted electrochemical measurements that the functionalized fibers showed a 132.8% increase in specific capacitance compared to non-functionalized fibers.Dye-adsorption test and the obtained Randles-Sevcik plot demonstrated that the oxygen plasma functionalized fibers exhibited increased surface area.It was further established by Brunauer-Emmett-Teller(BET)measurements that the surface area of the CNT fibers was increased from 168.22 m^2/g to 208.01 m^2/g after plasma functionalization.The pore size distribution of the fibers was also altered by this processing.The improved electrochemical data was attributed to enhanced wettability,increased surface area,and the presence of oxygen functional groups,which promoted the capacitance of the fibers.Fiber supercapacitors were fabricated from the oxygen plasma functionalized CNT fiber electrodes using different electrolyte systems.The devices with functionalized electrodes exhibited excellent cyclic stability(93.2% after 4000 cycles),flexibility,bendability,and good energy densities.At 0.5 m A/cm^2,the EMIMBF4 device revealed a specific capacitance,which is 27% and 65%greater than the specific capacitances of devices using EMIMTFSI and H2SO4 electrolytes,respectively.The practiced in this work plasma surface processing can be employed in other applications where fibers,yarns,ribbons,and sheets need to be chemically modified.

Directional Oxygen Functionalization by Defect in Different Metamorphic-Grade Coal-Derived Carbon Materials for Sodium Storage

As the limiting factor for an energy storage technique from lab-scale to industrial-scale,cost means not only the price of raw materials but also the simplicity of processing technics.In this work,the oxygen functionalized carbon materials were obtained from three representative different metamorphic-grade coals,that is,lignite,bitumite,anthracite.Oxygen functional groups like quinones,carboxylic anhydrides,and lactones are easier to form near defects according to the thermogravimetric-mass spectrometry measurements and density functional theory calculation.Considering the highest amount of defects and C=O contained functional groups,the low metamorphic-grade lignite derived carbon exhibits a reversible capacity of 259.7 mA h g^(-1)after 50 cycles at 0.03 A g^(-1),best among these micron sized coal-based carbons.The surface active sites contribute highly stable and majority of sodium storage capacity evidenced by in situ Raman spectra and cyclic voltammetry curves at different scan rates.The coal-based carbon materials in this work offer options for industrial applications of sodium-ion battery anode materials.

Enhancement of gaseous mercury(Hg^0) adsorption for the modified activated carbons by surface acid oxygen function groups

This article discussed the benzoic acid activated carbons which have changed the types and content of acid oxygen-function groups on the surface of activated carbons and their effect on the adsorption for Hg^0 in simulated flue gas at 140 ℃. These surface acid oxygen function groups were identified by Boehm titration, Fourier transformation infrared spectrum, temperature programmed desorption and X-ray photoelectron spectroscopy. It indicates that the carboxyl, lactone and phenolic were formed when the benzoic acid is loaded on the surface of activated carbons. Among the surface acid oxygen function groups, the carboxyl groups enhance the adsorption capacities of Hg^0 for activated carbons to a greater extent.

Structure evolution of oxygen removal from porous carbon for optimizing supercapacitor performance

The presence of oxygen functional groups is detrimental to the capacitive performance of porous carbon electrode in organic electrolyte. In this regards, hydrogen thermal reduction has been demonstrated effective approach in removing the unstable surface oxygen while maintaining the high porosity of carbon matrix. However, the exact evolution mechanism of various oxygen species during this process, as well as the correlation with electrochemical properties, is still under development. Herein, biomass-based porous carbon is adopted as the model material to trace its structure evolution of oxygen removal under hydrogen thermal reduction process with the temperature range of 400–800 °C. The optimum microstructure with low oxygen content of 0.90% and proper pore size distribution was achieved at 700°C. XPS, TPRMS and Boehm titration results indicate that the oxygen elimination undergoes three distinctive stages(intermolecular dehydration, hydrogenation and decomposition reactions). The optimum microstructure with low oxygen content of 0.90% and proper pore size distribution was achieved at 700 °C. Benefiting from the stable electrochemical interface and the optimized porous structure, the as-obtained HAC-700 exhibit significantly suppressed self-discharge and leak current, with improved cycling stability, which is attributable to the stabilization of electrochemical interface between carbon surface and electrolyte. The result provides insights for rational design of surface chemistry for high-performance carbon electrode towards advanced energy storage.

Umbilical cord-derived mesenchymal stem cell transplantation combined with hyperbaric oxygen treatment for repair of traumatic brain injury

Transplantation of umbilical cord-derived mesenchymal stem cells（UC-MSCs） for repair of traumatic brain injury has been used in the clinic. Hyperbaric oxygen（HBO） treatment has long been widely used as an adjunctive therapy for treating traumatic brain injury. UC-MSC transplantation combined with HBO treatment is expected to yield better therapeutic effects on traumatic brain injury. In this study, we established rat models of severe traumatic brain injury by pressurized fluid（2.5–3.0 atm impact force）. The injured rats were then administered UC-MSC transplantation via the tail vein in combination with HBO treatment. Compared with monotherapy, aquaporin 4 expression decreased in the injured rat brain, but growth-associated protein-43 expression, calaxon-like structures, and CM-Dil-positive cell number increased. Following combination therapy, however, rat cognitive and neurological function significantly improved. UC-MSC transplantation combined with HBO therapyfor repair of traumatic brain injury shows better therapeutic effects than monotherapy and significantly promotes recovery of neurological functions.

Neuroprotective effect of Shenqi Fuzheng injection pretreatment in aged rats with cerebral ischemia/reperfusion injury

Shenqi Fuzheng injection is extracted from the Chinese herbs Radix Astragali and Radix Codonopsis. The aim of the present study was to investigate the neuroprotective effects of Shenqi Fuzheng injection in cerebral ischemia and reperfusion. Aged rats（20–22 months） were divided into three groups： sham, model, and treatment. Shenqi Fuzheng injection or saline（40 m L/kg） was injected into the tail vein daily for 1 week, after which a cerebral ischemia/reperfusion injury model was established. Compared with model rats that received saline, rats in the treatment group had smaller infarct volumes, lower brain water and malondialdehyde content, lower brain Ca2＋ levels, lower activities of serum lactate dehydrogenase and creatine kinase, and higher superoxide dismutase activity. In addition, the treatment group showed less damage to the brain tissue ultrastructure and better neurological function. Our findings indicate that Shenqi Fuzheng injection exerts neuroprotective effects in aged rats with cerebral ischemia/reperfusion injury, and that the underlying mechanism relies on oxygen free radical scavenging and inhibition of brain Ca2＋ accumulation.

Study on the action and mechanism of humic acids in Kaschin-Beck disease

Humic acids, especially FA in fractions, contain more oxygen functional groups. In this experiment, on the basis of confirming the action of humic acids on KBD, what was studied is the biological effects of one of main oxygen functional groups, hydroxy group (-OH). The results indicate that inducing pathologic process of KBD, obviously decrease the GSH-Px activity and induce peroxidation membrane injury of tissue. The SOD activity increase in the tissues caused by oxygen functional groups showed that enhancing of free radical reaction should not be neglected.

Plasma activation towards oxidized nanocarbons for efficient electrochemical synthesis of hydrogen peroxide

Oxidized nanocarbons(ONCs)have been regarded as efficient electrocatalysts for H2O2 production.However,wet chemical procedures involving large volumes of strong acid and long synthetic time are usually needed to obtain these ONCs.Herein,a plasma activation strategy is developed as a rapid and environmentally benign approach to obtain various ONCs,including oxidized multiwalled carbon nanotubes,single-walled carbon nanotube,graphene,and super P carbon black.After a few minutes of plasma activation,oxygen-containing functional groups and defects can be effectively introduced onto the surface of nanocarbons.Enhanced electrocatalytic activity and selectivity are demonstrated by the plasma-ONCs for H2O2 production.Taking oxidized multiwalled carbon nanotubes as an example,high selectivity(up to 95%)and activity(0.75 V at 1 mA cm^(−2))can be achieved in alkaline solution.Moreover,ex situ x-ray photoelectron spectroscopy and in situ Raman measurements reveal that C–O,C=O,edge defect,and sp2 basal planar defect are probably the active sites.

A Spin-orbit Coupling Study on the Quinoline-and Porphyrin-based Photosensitizers

The spin-orbit coupling（SOC） of four porphyrin- and quinoline-based compounds has been studied using Pauli-Breit SOC operator with one- and two-electron terms. The results revealed that the yield of singlet oxygen is affected by the spin-orbit coupling matrix element involving the emitting triplet and the perturbing singlet state. Investigated quinoline-based compounds have more high SOC values than those porphyrin-based compounds due to spin parallel electron pairs of oxygen. The open shell d8 of metal Pt can induce the stronger exchange interactions than the closed shell p6 of metal Mg, resulting in bigger SOC matrix element in quinoline-based Pt complex than in the quinoline-based Mg complex. Simultaneously, potential energy curves of the first excited sate and the first triplet sate have been calculated, which proves that all investigated complexes can induce singlet oxygen. These computational findings support quinolin-based compounds have high singlet oxygen yields and provide a rigorous basis for predicting the probability of singlet oxygen yields in plane-type molecules.

Tuning Optical Properties of Graphene Oxide under Compressive Strain Using Wet Ball Milling Method

We report on the effect of compressive stress on the optical properties of graphene oxide using a wet ball milling technique. For this purpose, graphene oxide was prepared using the modified Hummer’s method and subsequently processed with wet ball milling. X-ray diffraction infers a peak at 9.655° which is the allowed reflection for the graphene oxide. The Williamson-Hall method is used to quantify the strain on the 10 hrs and 20 hrs ball milled graphene oxide samples and is found to be 4.2% and 4.8% respectively. Although we applied strain on the graphene oxide, it actually helped to reduce the defects which are confirmed by the intensity drop-off of D-peak in Raman spectroscopy. Indeed there exists a band gap alteration of 0.14 eV for an applied compressive strain of ~4.8%, hinting that the reduction in oxygen functional groups and the same is confirmed with the Fourier Transform Infrared Spectroscopy (FTIR). The present results would be helpful in developing graphene oxide based flexible memories and optoelectronic devices.

Tailoring biochar by PHP towards the oxygenated functional groups(OFGs)-rich surface to improve adsorption performance

In this work,a modification method of H_(3)PO_(4)plus H_(2)O_(2)(PHP)was introduced to targetedly form abundant oxygenated functional groups(OFGs)on biochar,and methylene blue(MB)was employed as a model pollutant for adsorption to reflect the modification performance.Results indicated that parent biochars,especially derived from lower temperatures,substantially underwent oxidative modification by PHP,and OFGs were targetedly produced.Correspondingly,approximately 21.5-fold MB adsorption capacity was achieved by PHP-modified biochar comparing with its parent biochar.To evaluate the compatibility of PHP-modification,coefficient of variation(CV)based on MB adsorption capacity by the biochar from various precursors was calculated,in which the CV of PHP-modified biochars was 0.0038 comparing to0.64 of the corresponding parent biochars.These results suggested that the PHP method displayed the excellent feedstock compatibility on biochar modification.The maximum MB adsorption capacity was454.1 mg/g when the H_(3)PO_(4)and H_(2)O_(2)fraction in PHP were 65.2%and 7.0%;the modification was further intensified by promoting temperature and duration.Besides,average 94.5%H_(3)PO_(4)was recovered after 10-batch modification,implying 1.0 kg H_(3)PO_(4)(85%)in PHP can maximally modify 2.37 kg biochar.Overall,this work offered a novel method to tailor biochar towards OFGs-rich surface for efficient adsorption.

Ozone-Mediated Functionalization of Multi-Walled Carbon Nanotubes and Their Activities for Oxygen Reduction Reaction

The functionalization of multi-walled carbon nanotubes （MWCNTs） by ozone treatment has been sys- tematically investigated by using Raman spectroscopy, transmission electron microscopy （TEM）, Fourier transform inhared spectroscopy （FTIR）, X-ray photoelectron spectroscopy （XPS）, organic elemental anal- ysis （OEA） and Boehm titration. The results showed that the functionalization process occurred at defective sites （opened mouths, tube caps, debris, etc.） before opening caps and truncating walls, and finally the graphitic structure was deteriorated. The surface oxygen content first increased with the treatment time but kept at around 8.0 wt% after 5 h. The analysis of the distribution of oxygen-containing groups re- vealed that phenolic hydroxyl was gradually converted to carboxyl and lactone, The carboxyl was found to play a pivotal role to reduce the over-potentials when we used the functionalized MWCNTs as the cat- alyst for oxygen reduction reaction （ORR）.

High-performance Li-ion batteries based on graphene quantum dot wrapped carbon nanotube hybrid anodes

Since Akira Yoshino first proposed the usage of the carbonaceous materials as an anode of lithium ion batteries(LIBs)in 1985,carbonaceous materials such as graphite and graphene have been widely considered as LIB anodes.Here,we explored the application of novel carbonaceous UB anodes incorporating graphene quantum dots(GQDs).We fabricated a freestanding all-carbon electrode based on a porous carbon nanotube(CNT)sponge via a facile in-situ hydrothermal deposition technique,creating coaxial structure of GQD-coated CNTs(GQD@CNTs)through electrostatic interaction and n-n stacking with tunable loading and functionalization.This hybrid structure combined conductive CNTs with highly active GQDs,in which GQDs with predesigned functional groups provided massive storage sites for Li ions and the 3D CNT frameworks avoided the agglomeration of GQDs,together contributing to a high specific capacity(700 mAh·g^-1 at 100 mA·g^-1 after 100 cycles)and rate performance.Even at a high current density of 1,000 mA·g^-1,the reversible specific capacity remained at 483 mAh g-1 after 350 cycles.In particular,the mechanism study demonstrated the important role of oxygen functional groups of GQDs in promoting the performance of the LIB anodes by controlled grafting of GQDs onto various porous-carbon and metal-foam based structures.

Mechanism investigation of enhanced electrochemical H_(2)O_(2) production performance on oxygen-rich hollow porous carbon spheres

Electrochemical oxygen reduction is a promising approach for the sustainable decentralized production of H_(2)O_(2),but its viable commercialization is hindered by the insufficient development of efficient electrocatalysts.Here,we demonstrate a promising carbon-based catalyst,consisting of oxygen-rich hollow mesoporous carbon spheres(HMCSs),for selective oxygen reduction to H_(2)O_(2).The as-prepared HMCS exhibits high onset potential(0.82 V)and half-wave potential(0.76 V),delivering a significant positive shift compared with its oxygen-scarce counterparts and commercial Vulcan carbon.Moreover,excellent H2O2 selectivity(above 95%)and electrochemical stability(7%attenuation after 10 h operation)make this material a state-of-the-art catalyst for electrochemical H_(2)O_(2) production.The outstanding performance arises from a combination of several aspects,such as porous structure-facilitation of mass transport,large surface area,and proper distribution of oxygen-containing functional groups modification on the surface.Furthermore,the proposed oxygen reduction reaction(ORR)mechanism on HMCS surface reveals that-OH functional groups help promote the first electron transfer process while other oxygen modification facilitate the second electron transfer.

Hollow PtNi alloy nanospheres with enhanced activity and methanol tolerance for the oxygen reduction reaction

The development of active and methanol-tolerant cathode electrocatalysts for the oxygen reduction reaction （ORR） is extremely important for accelerating the commercial viability of direct methanol fuel cells （DMFCs）. In this work, we present an efficient and template-free route for facile synthesis of cyanide （CN^-）-functionalized PtNi hollow nanospheres （PtNi@CN HNSs） with a high alloying degree using a simple cyanogel reduction method at room temperature. The physical and electrocatalytic properties of the PtNi@CN HNSs were investigated by various physical and electrochemical techniques. The PtNi@CN HNSs exhibited significantly enhanced electrocatalytic activity, durability, and particular methanol tolerance for the ORR as compared to commercial Pt black, and thus they are promising cathode electrocatalysts for DMFCs.

Abnormal energy metabolism and tau phosphorylation in the brains of middle-aged mice in response to atmospheric PM2.5 exposure

In light of the accelerated aging of the global population and the deterioration of the atmosphere pollution, we sought to clarify the potential mechanisms by which fine particulate matter（PM_（2.5）） can cause cognitive impairment and neurodegeneration through the alteration of mitochondrial structure and function. The results indicate that PM_（2.5） inhalation reduces ATP production by disrupting the aerobic tricarboxylic acid cycle and oxidative phosphorylation, thereby causing the hypophosphorylation of tau in the cortices of middle-aged mice. Furthermore, excessive reactive oxygen species generation was involved in the impairment. Interestingly, these alterations were partially reversed after exposure to PM_（2.5） ended. These findings clarify the mechanism involved in mitochondrial abnormality-related neuropathological dysfunction in response to atmospheric PM_（2.5） inhalation and provide an optimistic sight for alleviating the adverse health outcomes in polluted areas.