中元古代昆阳群Fe-Cu-REE矿床地球化学研究-以武定迤纳厂矿床为例

稀土元素成矿与地壳的构造运动密切相关，稀土在中元古代具有大规模暴发性成矿特征。云南武定迤纳厂稀土铁铜矿床为昆阳群因民组出现稀土富集成矿的典型代表。本论文选择迤纳厂矿床为主要研究对象，系统研究矿床不同类型岩（矿）石和矿物的稀土元素地球化学特征，探讨富稀土的成矿流体、成矿物质来源和稀土元素成矿时代，揭示昆阳裂谷初期因民组稀土元素富集的地球化学机制。主要认识如下：1、迤纳厂矿床产于昆阳裂谷初期形成的禄丰一武定火山断陷盆地中。早中元古界昆阳群分布于绿汁江岩石圈断裂和小江一易门断裂的夹持地带，呈狭长状展布。迤纳厂矿床赋矿地层为昆阳群因民组上段的硅质白云岩和碱性火山岩（粗面安山岩）。矿体产出形态和矿石的结构构造等均显示矿体与赋矿地层同沉积特征；出现独立矿物氟碳饰矿、独居石及褐帘石，磷灰石、萤石、菱铁矿等矿物中也含有一定量的稀土，沿矿体走向和垂向稀土元素变化不大。2、矿体顶、底板围岩（石榴石黑云母片岩、钠长黑云母片岩等）的原岩为碱性火山岩（粗面安山岩），相对富集大离子亲石元素Ba、Cs、Rb、K、LRE日及贫Zr、Sr、Ti、Hf、HEE，为早元古代末期一中元古代早期交代富集地慢低程度部分熔融所形成的碱性火山岩。矿石稀土总量高（645-4443）×10-6，强烈富集轻稀土（（La/Tb）N＝17.3-81.1），稀土元素分布特征明显不同于矿区正常沉积的硅质白云岩和后期侵入的钠长石英斑岩及火山角砾岩，而与矿体顶、底板碱性火山岩中稀土元素配分特征基本一致，暗示稀土成矿物质来源与碱性火山岩有密切的关系；3、矿石中微量元素组合及变化特征与现代海底正在喷出的热液和热液沉积物中元素组合有较大的可比性，明显不同与火成碳酸岩型稀土矿床中的特征元素组合；在微量元素判别图解（Al-Fe-Mn、Fe／Ti-Al／（Al+Fe＋Mn）、U-Th、Y-P2O5等）中，逸纳厂矿石均投影在热水沉积区，矿石的Y／Ho值与黑烟囱值接近，表明成矿流体为高温、还原性质，稀土成矿可能以热水沉积作用方式为主；4、对矿石中主要矿物萤石、菱铁矿、磁铁矿、石英、方解石的稀土元素特征研究表明，矿石沉积时不同矿物中稀土元素分布特征基本相同，主要受成矿流体中稀土分布特征制约。而后期变质作用形成的矿物，其稀土元素分布主要受矿物晶体结构控制。同期成矿流体从早期到晚期（块状矿石→条带状矿石），轻重稀土分异变小，稀土总量增加，条带状矿石中稀土含量最高；矿石黄铜矿6345值变化在一任3％0到2g％。范围，显示慢源硫特征；菱铁矿6r3C（8％-9.1%）、δ18O（-11.17%-15.37）‰指示成矿流体具岩浆来源和有机质的脱梭酸分解作用参与；成矿流体中稀土元素可能主要以（RE（CO3）3F）4-、（既（CO3）3F2）、（RE（F，Cl万等形式迁移，当温度降低时沉淀出氟碳饰矿等稀土矿物；5、矿石和萤石单矿物 Sm-Nd等时线年龄分别为1621士110Ma和15：38士43Ma，与矿区碱性火山岩错石的U-Pb年龄1676Ma、因民组顶部石英正长斑岩的错石U-P1。年龄1685Ma基本一致，也与因民组地层年龄1765M。较为接近，反映成矿时代为早元古代晚期和中元古代早期：这一时间也与一早元古代晚期一中元古代早期昆阳裂谷初始裂陷阶段，大量来自于地幔的碱性火山岩喷发事件相吻合。矿石。Nd（t）:-2.87-3.60，萤石单矿物εNd（t）：-3.93-5.90，变化范围较窄并全为负值，接近0，指示源区为富集地幔。同时结合矿床形成的构造一地质环境及矿体产出的地质形态，认为逛纳厂稀土铁铜矿床可能是在昆阳裂谷初期，在碱性火山岩浆喷发的间歇期，来自地幔富稀土、挥发份的成矿流体由火山喷流一同生沉积方式形成的矿床。6、昆阳群因民组地层中出现的稀土富集、成矿与我国的白云鄂博稀土REE-Fe-Nb超大型矿一床和澳大利亚的olympic Dam Cu-U-Au-Ag-REE超大型矿床，在成矿时代、产出大地构造背景、成矿物质来源等方面具有较大的相似性，均体现成矿受控于中元古代1.5Ga超大陆聚合前或随后裂解初始阶段伴随的非造山型碱性岩浆或热液作用，稀土来源于超大陆拼合前因板块俯冲交代而形成的富集地幔。

海洛因成瘾者的注意偏向及其脑电机制

行为学研究显示，对毒品相关刺激的注意偏向是海洛因成瘾者的认知特点。本文介绍的一系列实验室研究，试图借助成熟的认知心理学研究方法，深入探讨这个现象。首先，在先期实验中，考虑到配对图片的情绪色彩的情况下，利用点－探测范式复制出注意偏向的现象。在此基础上，借助事件相关电位技术，利用提示－靶刺激范式试图为毒品相关性注意偏向提供一些电生理证据，并验证了诱因-敏化理论。 本文的主要结论是： 1、中国黄种人中的海洛因成瘾者也存在着对毒品相关刺激的注意偏向，为前人研究提供了跨种族、跨文化的支持性证据。 2、在控制了配对图片的情绪色彩之后，成瘾者仍然表现出对毒品线索的注意偏向。 3、首次为海洛因成瘾者对毒品相关刺激的注意偏向提供了较为严谨的电生理学依据。毒品线索视觉提示对其后的视觉加工具有调节作用。这种调节作用表现在ERP上，是对顶枕部P1波幅的调节。毒品相关注意偏向引发的偏差行为，很可能源于偏差了的感觉加工。 4、行为学数据与脑电数据显示出高度的一致性：海洛因成瘾者的注意偏向发生在脱离（Disengagement）阶段，而没有发生在投放（Engagement）阶段，即成瘾者的注意力更不愿意从毒品处脱离而不是毒品信息更容易攫取他们的注意力。这一结果验证了诱因-敏化理论，证实毒品线索会诱发成瘾者对毒品的病理性欲望（Wanting）。 5、海洛因成瘾者对毒品线索注意偏向的程度受成瘾时间、戒毒次数及其控制力的影响。

内源性注意与外源性注意神经机制的渐合假说

The relationship between exogenous attention and endogenous attention is still unclear. We conclude the result of previous studies and our experiments by proposing a convergence hypothesis. A lot of evidences from ERP and fMRI proved the distinction between exogenous and endogenous attention. The distinction is fit for the complicated surroundings. Some studies found that exogenous and endogenous attention activated some common brain areas but if there’s any common function in these areas was still unclear. Previous studies failed to disentangle the relationship between these two mechanisms in detail, and most of the previous studies compared these two mechanisms separately. We used the cue-target paradigm, controlled the SOA and the cue validity to separate endogenous and exogenous attention. We try to figure out the relationship between endogenous and exogenous attention. We found that, in the exogenous attention condition, the amplitude of the P1 component was larger and the amplitude of N1 was smaller than that in the invalid trials. In the endogenous attention condition, the amplitudes of the P1 and N1 components in valid trials were both larger than that in the invalid trials. The difference wave of endogenous and exogenous attentions showed that at the beginning of their process endogenous and exogenous attentions were separate and then the process was going to converge. The stimuli appear in the visual field will activate the “external trigger” in exogenous attention processing, and then the signal will be transferred to next stage, in the endogenous attention processing, when the observer want to attend, the “inner trigger” will be activated and the signal will be transfered. The difference between “external trigger” and “inner trigger” in endogenous and exogenous attention was significant, so the difference at the beginning of the process was significant. When the signal was transferred to the next processing stage, the difference between the endogenous and exogenous attention became diminished, and it was a convergence process. We used the cue-target paradigm, let the central cue and peripheral cue appear in one trial, try to investigate the relationship between endogenous and exogenous attention under different perceptual load conditions. The result from of difference wave showed that the relationship between the two attentions was consistent with the convergence hypothesis. We also found that under different perceptual load conditions, the relationship between endogenous and exogenous attention was different. The perceptual load has influence on the “external trigger” and “inner trigger”. A cue-target paradigm was used to investigate the relationship between attention, age and perceptual load, we found that the function of visual attention was decrease in the old group, they need more attentional resource when they face the issue. The aging effect has influence on the “external trigger” and “inner trigger”. The effects of age and perceptual load were much higher in exogenous attention condition.

On the Origin of Power Laws in Internet Topologies

Recent empirical studies have shown that Internet topologies exhibit power laws of the form for the following relationships: (P1) outdegree of node (domain or router) versus rank; (P2) number of nodes versus outdegree; (P3) number of node pairs y = x^α within a neighborhood versus neighborhood size (in hops); and (P4) eigenvalues of the adjacency matrix versus rank. However, causes for the appearance of such power laws have not been convincingly given. In this paper, we examine four factors in the formation of Internet topologies. These factors are (F1) preferential connectivity of a new node to existing nodes; (F2) incremental growth of the network; (F3) distribution of nodes in space; and (F4) locality of edge connections. In synthetically generated network topologies, we study the relevance of each factor in causing the aforementioned power laws as well as other properties, namely diameter, average path length and clustering coefficient. Different kinds of network topologies are generated: (T1) topologies generated using our parametrized generator, we call BRITE; (T2) random topologies generated using the well-known Waxman model; (T3) Transit-Stub topologies generated using GT-ITM tool; and (T4) regular grid topologies. We observe that some generated topologies may not obey power laws P1 and P2. Thus, the existence of these power laws can be used to validate the accuracy of a given tool in generating representative Internet topologies. Power laws P3 and P4 were observed in nearly all considered topologies, but different topologies showed different values of the power exponent α. Thus, while the presence of power laws P3 and P4 do not give strong evidence for the representativeness of a generated topology, the value of α in P3 and P4 can be used as a litmus test for the representativeness of a generated topology. We also find that factors F1 and F2 are the key contributors in our study which provide the resemblance of our generated topologies to that of the Internet.

The role of glucocorticoid-induced tumour necrosis factor receptor in developing mouse sympathetic neurons

Hereditary sensory autonomic neuropathy IV (HSAN IV) is an autosomal recessive disorder characterised by inability to feel pain and anhidrosis and is a consequence of defective NGF/TrkA signalling and growth of sensory and sympathetic neurons. Glucocortiocoid-induced tumour necrosis factors receptor (GITR), a transmembrane protein, activated by its specific ligand, GITRL, is well known for its role in the regulation of innate and acquired immune system responses. Recently, GITR was found to be required for NGF-dependant and extracellular signal-related kinase 1/2 (ERK1/2)-induced neurite growth and target innervation in the developing sympathetic nervous system (SNS). Given this novel role of GITR, it is possible that strategies targeting GITR have potential therapeutic benefit in promoting neurite growth in autonomic neuropathies such as HSAN IV. Using P1 mouse SCG neurons as a model, in addition to various SCG cell treatments, knock down models and transfection methods, we investigated whether GITR increases the sensitivity of sympathetic neurons to NGF; the region of GITR required for the enhancement of NGF-promoted growth, the signalling pathways downstream of GITR and how extensively GITR is involved in regulating peripheral innervation of the SNS. Results indicate that the region responsible for the growth promoting effects of GITR lies in its juxtamembrane intracellular region (here termed the growth promoting domain (GPD)) of GITR. The GPD of GITR activates ERK1/2 and inhibits nuclear factor kappa B (NF-κB) in an inverse fashion to provide an optimal cellular growth environment for P1 SCG neurons. While deleting the GPD of GITR had no effect on TrkA expression, constitutive phosphorylation of specific sites in the GPD reduced TrkA expression indicating a possible role for GITR in increasing the sensitivity of SCG neurons to NGF by the regulation of these sites, TrkA expression and subsequent NGF/TrkA binding. GITR appears to be heterogeneously required for NGF-promoted target innervation of SCG neurons in some organs, implying additional factors are involved in extensive NGF-target innervation of the SNS. In conclusion, this study answers basic biological questions regarding the molecular mechanism behind the role of GITR in the development of the SNS, and provides a basis for future research if GITR modulation is to be developed as a strategy for promoting axonal growth.

Novel ingredients from brewers' spent grain - bioactivity in cell culture model systems and bioactivity retention in fortified food products

Functional food ingredients, with scientifically proven and validated bioactive effects, present an effective means of inferring physiological health benefits to consumers to reduce the risk of certain diseases. The search for novel bioactive compounds for incorporation into functional foods is particularly active, with brewers’ spent grain (BSG, a brewing industry co-product) representing a unique source of potentially bioactive compounds. The DNA protective, antioxidant and immunomodulatory effects of phenolic extracts from both pale (P1 - P4) and black (B1 – B4) BSG were examined. Black BSG extracts significantly (P < 0.05) protected against DNA damage induced by hydrogen peroxide (H2O2) and extracts with the highest total phenolic content (TPC) protected against 3-morpholinosydnonimine hydrochloride (SIN-1)-induced oxidative DNA damage, measured by the comet assay. Cellular antioxidant activity assays were used to measured antioxidant potential in the U937 cell line. Extracts P1 – P3 and B2 - B4 demonstrated significant (P < 0.05) antioxidant activity, measured by the superoxide dismutase (SOD) activity, catalase (CAT) activity and gluatathione (GSH) content assays. Phenolic extracts P2 and P3 from pale BSG possess anti-inflammatory activity measured in concanavalin-A (conA) stimulated Jurkat T cells by an enzyme-linked immunosorbent assay (ELISA); significantly (P < 0.05) reducing production of interleukin-2 (IL-2), interleukin-4 (IL-4, P2 only), interleukin-10 (IL-10) and interferon-γ (IFN-γ). Black BSG phenolic extracts did not exhibit anti-inflammatory effects in vitro. Hydroxycinnamic acids (HA) have previously been shown to be the phenolic acids present at highest concentration in BSG; therefore the HA profile of the phenolic extracts used in this research, the original barley (before brewing) and whole BSG was characterised and quantified using high performance liquid chromatography (HPLC). The concentration of HA present in the samples was in the order of ferulic acid (FA) > p-coumaric acid (p-CA) derivatives > FA derivatives > p-CA > caffeic acid (CA) > CA derivatives. Results suggested that brewing and roasting decreased the HA content. Protein hydrolysates from BSG were also screened for their antioxidant and anti-inflammatory potential. A total of 34 BSG protein samples were tested. Initial analyses of samples A – J found the protein samples did not exert DNA protective effects (except hydrolysate H) or antioxidant effects by the comet and SOD assays, respectively. Samples D, E, F and J selectively reduced IFN-γ production (P < 0.05) in Jurkat T cells, measured using enzyme linked immunosorbent assay (ELISA). Further testing of hydrolysates K – W, including fractionated hydrolysates with molecular weight < 3, < 5 and > 5 kDa, found that higher molecular weight (> 5 kDa) and unfractionated hydrolysates demonstrate greatest anti-inflammatory effects, while fractionated hydrolysates were also shown to have antioxidant activity, by the SOD activity assay. A commercially available yogurt drink (Actimel) and snack-bar and chocolate-drink formulations were fortified with the most bioactive phenolic and protein samples – P2, B2, W, W < 3 kDa, W < 5 kDa, W > 5 kDa. All fortified foods were subjected to a simulated gastrointestinal in vitro digestion procedure and bioactivity retention in the digestates was determined using the comet and ELISA assays. Yogurt fortified with B2 digestate significantly (P < 0.05) protected against H2O2-induced DNA damage in Caco-2 cells. Greatest immunomodulatory activity was demonstrated by the snack-bar formulation, significantly (P < 0.05) reducing IFN-γ production in con-A stimulated Jurkat T cells. Hydrolysate W significantly (P < 0.05) increased the IFN-γ reducing capacity of the snack-bar. Addition of fractionated hydrolysate W < 3 kDa and W < 5 kDa to yogurt also reduced IL-2 production to a greater extent than the unfortified yogurt (P < 0.05).

Estudios preliminares para la elaboración de modelos de respuesta a la aplicación de fósforo en el sud este bonaerense, bajo condiciones de invernáculo

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Cambios en las fracciones de fósforo de un suelo entisol durante procesos de mineralización y agotamiento

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Effect of reflow profile and thermal cycle ageing on the intermetallic formation and growth in lead-free soldering

The formation and growth of intermetallic compound layer thickness is one of the important issues in search for reliable electronic and electrical connections. Intermetallic compounds (IMCs) are an essential part of solder joints. At low levels, they have a strengthening effect on the joint; but at higher levels, they tend to make solder joints more brittle. If the solder joint is subjected to long-standing exposure of high temperature, this could result in continuous growth of intermetallic compound layer. The brittle intermetallic compound layer formed in this way is very much prone to fracture and cold therefore lead to mechanical and electrical failure of the joint. Therefore, the primary aim of this study is to investigate the growth of intermetallic compound layer thickness subjected to five different reflow profiles. The study also looks at the effect of three different temperature cycles (with maximum cycle temperature of 25 0C, 40 0C and 60 0C) on intermetallic compound formation and their growth behaviour.. Two different Sn-Ag-Cu solder pastes (namely paste P1 and paste P2) which were different in flux medium, were used for the study. The result showed that the growth of intermetallic compound layer thickness was a function of ageing temperature. It was found that the rate of growth of intermetallic compound layer thickness of paste P1 was higher than paste P2 at the same temperature condition. This behaviour could be related to the differences in flux mediums of solder paste samples used.

The effect of wall-slip formation on the rheological behaviour of lead-free solder pastes

Wall-slip plays an important role in the flow behaviour of solder paste materials. The wall-slip arises due to the various attractive and repulsive forces acting between the solder particles and the walls of the measuring geometry. These interactions could lead to the presence of a thin liquid layer adjacent to the wall, which causes slippage. The aim of this study is to investigate the influence of the solder paste formulation on wall-slip formation and its effect on the printability of these pastes material. A wall slip model is utilised to calculate the true viscosity and slip velocity for the lead-free solder pastes samples used in this study. The difference in the measured viscosity and the true viscosity could indicate wall-slip formation between the solder pastes and the parallel plate. Sample P1 showed a higher slip velocity compared to sample P2. The slip velocity calculated for the solder pastes could be used as a performance indicator to understand the paste release characteristics in the stencil printing process.

Study of the rheological behaviour of Sn-Ag-Cu solder pastes and their correlation with printing performance

Solder paste plays an important role in the electronic assembly process by providing electrical, mechanical and thermal bonding between the components and the substrate. The rheological characterisation of pastes is an important step in the design and development of new paste formulations. With the ever increasing trend of miniaturisation of electronic products, the study of the rheological properties of solder pastes is becoming an integral part in the R&D of new paste formulations and in the quality monitoring and control during paste manufacture and electronic assembly process. This research work outlines some of the novel techniques which can be successfully used to investigate the rheology of leadfree solder pastes. The report also presents the results of the correlation of rheological properties with solder paste printing performance. Four different solder paste samples (namely paste P1, P2, P3 and P4) with different flux vehicle systems and particle size distributions were investigated in the study. As expected, all the paste samples showed shear thinning behaviour. Although the samples displayed similar flow behaviour at high shear rates, differences were observed at low shear rates. In the stencil printing trials, round deposits showed better results than rectangular deposits in terms of paste heights and aperture filling. Our results demonstrate a good correlation between higher paste viscosity and good printing performance. The results of the oscillatory and thixotropy tests were also successfully correlated to the printing behaviour of solder paste.

Vibrational spectra and crystal structure of the di-amino acid peptide cyclo(L-Met-L-Met): Comparison of experimental data and DFT calculations

Experimental Raman and FT-IR spectra of solid-state non-deuterated and N-deuterated samples of cyclo(L-Met-L-Met) are reported and discussed. The Raman and FT-IR results show characteristic amide I vibrations (Raman: 1649 cm-1, infrared: 1675 cm-1) for molecules exhibiting a cis amide conformation. A Raman band, assigned to the cis amide II vibrational mode, is observed at sim1493 cm-1 but no IR band is observed in this region. Cyclo(L-Met-L-Met) crystallises in the triclinic space group P1 with one molecule per unit cell. The overall shape of the diketopiperazine (DKP) ring displays a (slightly distorted) boat conformation. The crystal packing employs two strong hydrogen bonds, which traverse the entire crystal via translational repeats. B3-LYP/cc-pVDZ calculations of the structure of the molecule predict a boat conformation for the DKP ring, in agreement with the experimentally determined X-ray structure. Copyright © 2009 John Wiley & Sons, Ltd.

Ocean climate anomalies and the ecology of the North Sea

Long-term changes in the plankton of the North Sea are investigated using data from the continuous plankton recorder (CPR) survey. During the last 4 decades, there appears to have been 2 large anomalous periods within the plankton data set, one that occurred in the late 1970s and the other in the late 1980s. These anomalous periods seem to be largely synchronous with unusual ocean climate conditions that have occurred episodically over a timescale of decades. The unusual ocean climate conditions prevailing at these 2 time periods appear to contain important hydrographical elements that involve oceanic incursions into the North Sea. This paper, using data from the CPR survey and providing evidence from other studies, focuses on the relationship between the long-term changes in the biology of the North Sea and these 2 exceptional hydro-climatic events. Here, we suggest that while atmospheric variability and associated changes in regional temperatures have a dominant effect on the marine environment, oceanic influences on the ecology of a semi-closed environment such as the North Sea may have been underestimated in the past.

Oxygen photolysis in the Mauritanian upwelling: Implications for net community production

We carried out 16 photochemical experiments of filtered surface water in a custom-built solar simulator and concomitant measurements of in vitro gross primary production (GPP) and respiration (R) in the Mauritanian upwelling during a Lagrangian study following three sulfur hexafluoride–labeled patches of upwelled water (P1 to P3). Oxygen photolysis rates were correlated with the absorbance of chromophoric dissolved organic matter (CDOM) at 300 nm, suggesting first-order kinetics with respect to CDOM. An exponential fit was used to calculate the apparent quantum yield (AQY) for oxygen photolysis, giving an average AQY of 0.00053 µmol O2 (mole photons m−2 s−1)−1 at 280 nm and slope of 0.0012 nm−1. Modeled photochemical oxygen demand (POD) at the surface (3–16 mmol m−3 d−1) occasionally exceeded R and was dominated by ultraviolet radiation (71–79%). Euphotic-layer integrated GPP decreased with time during both P-1 and P-3, whereas R remained relatively constant and POD increased during P-1 and decreased during P-3. On Day 4 of P-3, GPP and POD maxima coincided with high CDOM absorbance, suggesting “new” CDOM production. Omitting POD may lead to an underestimation of net community production (NCP), both through in vitro and geochemical methods (here by 2–22%). We propose that oxygen-based NCP estimates should be revised upward. For the Mauritanian upwelling, the POD-corrected NCP was strongly correlated with standard NCP with a slope of 1.0066 ± 0.0244 and intercept of 46.51 ± 13.15 mmol m−2 d−1.

Retinal Pigment Epithelial Cell DNA is Damaged by Exposure to Benzo[a]pyrene, a Constituent of Cigarette Smoke.

This study examined the effect of exogenous benzo[ a ]pyrene (BaP), an important constituent of cigarette smoke, on cultured bovine retinal pigment epithelial (RPE) cells. Evidence is presented for its metabolic conversion into benzo[ a ]pyrene diol epoxide (BPDE) and the consequent formation of potentially cytotoxic nucleobase adducts in DNA. Cultured RPE cells were treated with BaP at concentrations in the range of 0–100 µm. The presence of BaP was found to cause inhibition of cell growth and replication. BaP induced the expression of a phase I drug metabolizing enzyme which was identified as cytochrome P450 1A1 (CYP 1A1) by RT–PCR and by Western blotting. Coincident with the increased expression of CYP 1A1, covalent adducts between the mutagenic metabolite BPDE and DNA could be detected within RPE cells by immunocytochemical staining. Additional support for their formation was afforded by nuclease P1 enhanced 32P-postlabelling assays on cellular DNA. Single-cell gel electrophoresis (comet) assays showed that exposure of RPE cells to BaP rendered them markedly more susceptible to DNA damage induced by broad band UVB or blue light laser irradiation. In the case of UVB, this is consistent with the photosensitization of DNA cleavage by nucleobase adducts of BPDE. Collectively, these findings imply that BaP has a significant impact on RPE cell pathophysiology and suggest mechanisms whereby exposure to cigarette smoke might cause RPE dysfunction and cell death, thus possibly contributing to degenerative disorders of the retina.