This thesis consists of two parts. The first part deals with the magnetic properties of Fe3O4 nanocrystals and their possible application in water remediation. The second part is on the delamination of layered materials and the preparation of new layered hybrids from the delaminated sheets. In recent years, nanoscale magnetic particles have attracted considerable attention because of their potential applications in industry, medicine and environmental remediation. The most commonly studied magnetic nanoparticles are metals, bimetals and metal oxides. Of these, magnetite, Fe3O4, nanoparticles have been the most intensively investigated as they are, non-toxic, stable and easy to synthesize. Magnetic properties of nanoparticles such as the saturation magnetization, coercivity and blocking temperature are influenced both by size and shape. Below a critical size magnetic particles can become single domain and above a critical temperature (T B , the blocking temperature) thermal fluctuations can induce random flipping of magnetic moments resulting in loss of magnetic order. At temperatures above the blocking temperature the particles are superparamagnetic. Magnetic nanocrystals of similar dimensions but with different shapes show variation in magnetic properties especially in the value of the blocking temperature, because of differences in the surface anisotropy contribution. The properties of magnetic nanoparticles are briefly reviewed in Chapter 1. The objective of the present study was to synthesize Fe3O4 nanocrystals of different morphologies, to understand the difference in magnetic properties associated with shape and to explore the possibility of using Fe3O4 nanocrystals in water remediation. In the present study, oleate capped magnetite (Fe3O4) nanocrystals of spherical and cubic morphologies of comparable dimensions (∼10nm) have been synthesized by thermal decomposition of FeOOH in high-boiling octadecene solvent (Chapter 2). The nanocrystals were characterized by XRD, TEM and XPS spectroscopy. The nanoparticles of different morphologies exhibit very different blocking temperatures. Cubic nanocrystals have a higher blocking temperature (T B = 190 K) as compared to spheres (T B = 142 K). From the shift in the hysteresis loop it is demonstrated that the higher blocking temperature is a consequence of exchange bias or exchange anisotropy that manifests when a ferromagnetic material is in physical contact with an antiferromagnetic material. In nanoparticles, the presence of an exchange bias field leads to higher blocking temperatures T B because of the magnetic exchange coupling induced at the interface between the ferromagnet and antiferromagnet. It is shown that in these iron oxide nanocrystals the exchange bias field originates from trace amounts of the antiferromagnet wustite, FeO, present along with the ferrimagnetic Fe3O4 phase. It is also shown that the higher FeO content in nanocrystals of cubic morphology is responsible for the larger exchange bias fields that in turn lead to a higher blocking temperature. Magnetic nanoparticles with moderate magnetization can be easily separated from dispersions by applying low intensity magnetic fields. Oleate capped spherical and cubic iron oxide nanocrystals have considerable magnetic moment and hence have the potential as host-carriers for magnetic separation in environmental remediation. These nanocrystals are, however, dispersible only in non-polar solvents like chloroform, toluene, etc. Environmental remediation requires that the nanocrystals be water dispersible. This was achieved by functionalizing the surface of the iron oxide nanocrystals by coordinating carboxymethyl-β-cyclodextrin (CMCD) cavities (Chapter 3). The hydroxyl groups located at the rim of the anchored cyclodextrin cavity renders the surface of the functionalized nanocrystal hydrophilic. The integrity of the anchored CMCD molecules are preserved on capping and their hydrophobic cavities available for host-guest chemistry. The CMCD capped iron oxide particles are water dispersible and separable in modest magnetic fields (<0.5 T). Small molecules like naphthalene and naphthol can be removed from aqueous media by forming inclusion complexes with the anchored cavities of the CMCD-Fe3O4 nanocrystals followed by separation of the nanocrystals by application of a magnetic field. The adsorption properties of the iron oxide surface towards arsenic ions are unaffected by the CMCD capping so it too can be simultaneously removed in the separation process. To extend the application of the iron oxide nanocrystals so that they can both capture and destroy organic contaminants present in water, cyclodextrin functionalized water dispersible core-shell Fe3O4@TiO2 (CMCD-Fe3O4@TiO2) nanocrystals have been synthesized (Chapter 4). The application of these particles for the photocatalytic degradation of endocrine disrupting chemicals (EDC), bisphenol A and dibutyl phthalate, in water is demonstrated. EDC molecules that may be present in water are captured by the CMCD-Fe3O4@TiO2 nanoparticles by inclusion within the anchored cavities. Once included they are photocatalytically destroyed by the TiO2 shell on UV light illumination. The magnetism associated with the crystalline Fe3O4 core allows for the magnetic separation of the particles from the aqueous dispersion once photocatalytic degradation is complete. An attractive feature of these ‘capture and destroy’ nanomaterials is that they may be completely removed from the dispersion and reused with little or no loss of catalytic activity. The second part of the thesis deals with the intercalation of surfactants in inorganic layered solids and their subsequent delamination of the functionalized solid in non-polar solvents. The solids investigated were - the anionic layered double hydroxides (LDH), the 2:1 smectite clay, montmorillonite (MMT), layered metal thiophosphates (CdPS3) and graphite oxide (GO). Layered Double Hydroxides (LDH) are lamellar solids of the general chemical formula [M0(1−x)Mx(OH)2], where M0 is a divalent metal ion and M a trivalent ion. The structure of the Mg-Al layered double hydroxide (Mg-Al LDH) may be derived from that of brucite, Mg(OH)2, by isomorphous substitution of a part of the Mg2+ by trivalent Al3+ ions with electrical neutrality maintained by interlamellar exchangeable ions like nitrate or carbonate. The ion exchange intercalation of the anionic surfactant dodecyl sulfate (DDS) in an Mg-Al LDH and the subsequent delamination of the surfactant intercalated LDH in non-polar solvent is reviewed in Chapter 5. Delamination results in a clear dispersion of neutral nanosheets. The delaminated sheets are neutral as the surfactant chains remain anchored to the inorganic sheet. On solvent evaporation, the sheets re-stack to give back the original surfactant intercalated solid. This strategy for delamination of layered solids by intercalation of an appropriate surfactant followed by dispersing in a non-polar solvent has been extended to montmorillonite (MMT) and cadmium thiophosphates (CdPS3) by ion-exchange intercalation of the cationic surfactant dioctadecyldimethylammonium bromide (DODMA) followed by sonication in non-polar solvents e.g. toluene or chloroform as in the case of the LDH (Chapter 6). The nanosheets of the MMT and CdPS3 are electrically neutral as the surfactant chains remain anchored to the inorganic sheet even after exfoliation. Graphite oxide (GO) too can be delaminated by functionalizing the sheets by covalently linking oleylamine chains to the GO sheets via an amide bond. The oleylamine functionalized GO is easily delaminated in non-polar solvents to give electrically neutral GO nanosheets. It is shown in Chapter 7 that the 1:1 mixtures of dispersions of montmorillonite-DODMA with Mg-Al LDH-DDS nanosheets can self assemble, on solvent evaporation, to give a new layered solid with periodically alternating montmorillonite and LDH layers. In this method attractive forces between the neutral exfoliated nanosheets of cationic and anionic ensures self-assembly of a perfectly periodic alternating layered structure. The method has been extended to synthesize new layered solids in which surfactant tethered cationic and anionic inorganic sheets alternate. The hybrid solids synthesized are CdPS3—MgAl-LDH, CdPS3—CoAl-LDH, GO—MgAl-LDH, GO—CoAl-LDH. The procedure outlined in Chapter 7 allows for a simple, but versatile, method for generating new periodically ordered layered hybrid solids by self-assembly.

Over the last few decades, a vast research is going on, to study the optical properties of the nano particles i.e., metal and semiconductors thoroughly. Till date most of the optical studies are based on single particle measurement of a quantum dot (QD) or a chromophore under the influence of an external plasmonic field stimulus. In this the-sis, we tried to address the energy transfer at non local level on a layer of compact, monolayer QD assemblies over micro meter range. The energy transfer occurs in the presence of external field of metal particles or nanorods leads to the enhancement or quenching the emission from a layer of QDs. Chapter 1 is introduction to the basic theoretical aspects of excitons in semiconductor (QDs) and its optical properties under strong confinement regime. The discussion is followed with the optical properties of gold nanoparticles and rods, describing size and shape dependent variation of absorption properties, based on Mie and Mie-Gans theory. Theoretical background of collective effects in QD assemblies based on exciton-plasmonic interactions at single particle level as well as polarization based plasmo-nenhanced fluorescence has been subjected. Experimental techniques are explained in chapter 2 which contains the details of the synthesis of polymer capped nanoparticles with the respective characterization. A discussion on the synthesis methods for cadmium selenide QDs, gold nano particles and the rods with different polymer cap-ping legends and the related capping exchange methods. The thin film preparation of QD monolayers as well as hybrid nano assemblies using several techniques, i.e., Langmuir-Blodgett (LB), dip coat methods are provided. Further the details of surface morphology of the prepared thin films has been studied by different microscopic techniques i.e., atomic force microscopy (AFM), transmission electron microscopy (TEM) and scanning electron microscopy (SEM). The details of the PL emission measurements of these hybrid arrays using confocal, Raman and polarization based near field scanning optical microscope (NSOM) modes followed with the life time measurements. In third chapter, the substantial strong coupling and collective emission regime is engineered in the QD monolayer films embedded with tiny gold nano particles keeping the QD density same. Tuning the photoluminescence (PL) of semiconducting QD assemblies using small Au NPs in different ratio, different packing density and extent of spectral overlap between QD photoluminescence and the metal nanoparticle absorbance has been discussed. We provided possible experimental and theoretical evidence for the plasmon-mediated emergence of collective emission and enhanced quantum efficiency in these QD films with the consolidation of multiple emitters and multiple NPs. The quantum efficiency of these hybrid assemblies is further explored with different material as well as the size effect of metal nano particles. Chapter 4 comprises the experiment results of the self-assembled compact and partially aligned gold nano rod (GNR) arrays on QD monolayer films. We experimentally demonstrated the quantum efficiency of these QD hybrid assemblies is gaining max-imum when the longitudinal surface plasmon resonance (LSPR) absorption maxima of GNR arrays is resonant with the QD monolayer PL maxima and is always non-existent for the off resonant case. Further, we reported the variability in the size and morphology of these GNR domains leads to the maximum achieved enhancement as well as anisotropy value in comparison with isolated rods and the explored conditions to further enhance the efficiency in these QD hybrid assemblies.

Les ARN 5'-triphosphates (TP) et 5'-coiffés sont des molécules très convoitées des biologistes pour des études structurales par cristallographie ou comme outils thérapeutiques. Actuellement, ces oligonucléotides sont produits dans de faibles quantités via des procédés enzymatiques dépendants de la nature du nucléoside situé à l'extrémité 5'. Ces travaux se sont donc inscrits dans l'enjeu majeur de mettre au point une méthode chimique sur support solide qui permette l'accès à ces ARN 5'-fonctionnalisés en quantités importantes et sans restriction de séquences.Ce manuscrit rapporte une nouvelle méthode efficace de synthèse sur support solide d'ARN 5'-TP à grande échelle indépendante du nucléotide situé à l'extrémité 5' ou de la longueur de la séquence ARN. De plus, cette stratégie a été étendue avec quelques modifications à la synthèse d'analogues enzymatiquement plus stables de type: ARN 5'-β,γ-méthylène-TP, -(α-P-thio)-TP et -(α-P-thio)-(β,γ-méthylène)-TP.Une deuxième partie présente la synthèse supportée et l'évaluation antivirale de courts adénylates 2-5A 5'-TP portant des groupements enzymolabiles de type acétalesters en position 3' du ribose. Une dernière partie est consacrée à l'élaboration de nouvelles stratégies pour la synthèse d'ARN 5-coiffés. La première approche est un procédé en deux étapes où la structure coiffe (Gppp) est ajoutée sur support solide suivie d'une N7- méthylation enzymatique en solution, alors que la seconde est une méthode plus directe entièrement chimique. Par ailleurs, le couplage chimique de la coiffe sur les ARN supportés nécessite l'emploi d'un acide de Lewis. Ainsi l'utilisation de chlorures métalliques « verts » produits à partir de métaux de transition extraits de la biomasse a été évaluée dans la réaction du couplage de la coiffe sur les ARN. / 5'-triphosphates RNAand 5'-capped RNA are high valuable molecules which serve as important substrates for structural and mechanistic studies or drugs. To date, these oligonucléotides are produced by enzymatic process in low yields with a weak variability of the 5'-end. To overcome this bottleneck we aimed to develop a chemical access on solid-support of these 5'-functionalized RNA in great amount without any limitations in the RNA sequence.Here, a robust, reproducible, and scalable method for the solid-phase synthesis of 5′-triphosphate RNA is presented. Furthermore, this strategy was extended to produce enzymatic resistant analogs of the triphosphate counterpart like: 5'-β,γ-methylene-TP, -(α-P-thio)-TP et -(α-P-thio)-(β,γ-methylene)-TP RNA.In a second part, the solid-phase synthesis of short adenylates 2-5A 5'-TP bearing biolabile acetalester groups on nucleosides 3'-hydroxyls and their antiviral activities are described.Finally, we focused on developing two approaches for the production of 5'-capped RNA. One is a two-steps process which consists in the coupling of the cap structure on solid-support followed by an enzymatic N7-methylation in solution while the other one is a straightforward chemical strategy. Beside, the chemical coupling of the cap moiety on solid-supported RNA requires the use of Lewis acids. Then, the ability of « green » metal chlorides prepared from phytoextracted heavy metals to promote this reaction was studied.

第一筆金融交換出現以來，短短的十一、二年 場成長迅速，成為不可或 缺的財務工具。有鑑鷟艦瘣城竣@簡要的介紹，並建立金融交換之定 珓洶妨堨腄A主要承襲S. Sundaresan 對金融交bS. Sundaresan 的研究中 ，只針對一般的金融交A未考慮特殊型態的金融交換。所以本文的目的在B 下利率限制的金融交融之定價模型，主要定價的般的、capped、floored 、及 collared金融交換。漱隤k上，採用與其他研究不同的Feynman-Kac So- 融交換定價模型之前，必須先建立一般的金融交C再利用利率caps 和floors之特性，加入一般金融A以推導出有上下利率限制的金融交換定 價模型。F導出金融交換之定價模型外，並對所建立的模型k，計算出金融 交換和collar的價值，同時分析@般金融交換與collar金融交換的價值。 提供銀j眾，在進行金融交換時作為參考。

One major lesson derived from the implementation of the Endangered Species Act (ESA) over the past 30 years is that direct regulation is not the only nor the optimal way to protect endangered species on working lands because of an undue burden imposed on private landowners. The role of a voluntary conservation program is to rearrange incentives so that society bears the cost rather than the landowner. Employing a survey research methodology, I used theories of reasoned action and random choice to explore landowners? stated preferences for conservation programs. I found landowners? stated interest in compensation programs to be moderate at best. For those willing to consider programs involving endangered species, associating land management requirements for species conservation with direct benefits to the landowner is important, but perhaps not as important as ensuring that the program provides adequate financial incentives, consideration of the term of the program, and a level of certainty regarding the landowner?s future obligations under the ESA. Landowners are not a homogenous group. I identified two classes of landowners according to preferences for program structure. One group was highly sensitive to program structure, aside from financial incentives, while the other was likely to participate if adequately compensated with financial and technical assistance. These differences related to opinions on endangered species protection and dependence on their land for income. Voluntary incentive programs increasingly are a popular tool to maintain and enhance conservation; however, these programs are only successful insofar as landowners choose to enroll. This research demonstrates that improving recovery efforts on private lands requires program administrators to have a more complete understanding of landowners? views on endangered species and conservation programs in general, as well as their motivations for owning and operating their land. By doing so, programs with broader appeal and greater efficacy can be designed and implemented.

本論文含蓋三篇文章，分別從評價、避險和風險控管三方面，分析上限型股權連結保本票券。 第一篇文章為上限型股權連結保本票券之設計、評價和比較。本文考量投資人保守的投資行為與設限型股權連結票券所存在的delta跳躍(delta jump)現象，延伸Brennan and Schwartz (1976)模型，提出一個能在股價波動之際，使發行的避險部位delta呈現平滑變動且兼具保本(protected principal)功用的一般化模型(general form)。相較於一般的設限型股權連結保本模型，本模型具有以下特色。第一，加入股價成長率的調整因子(adjustable factor)，當景氣低靡，股價不停下跌時，正的調整因子可減緩股價下滑之勢，進而增加投資人在票券到期日時獲取更多資本利得(capital gain)的機會。同時，調整因子縮小了當期股價成長率與股價上限成長率(capped stock growth rate)之間的差距，繼而減緩delta 跳躍的幅度，降低發行者的避險成本。並且在HJM利率模型下，delta隨股價與股價波動度的變化更顯平滑(smooth)。第二，在保本率(protection rate)和參與率 (participation rate)不變之下，本模型的期初合理價格(fair price)較低，投資人能以較低的成本取得同等的投資保障。第三，若將本票券的名目面額(notional principal)視作共同基金(mutual fund)的淨值(net value)，而該淨值與股價連動，則本模型即成為股權連結的保本型基金(principal-protected fund)。 第二篇文章是路徑依賴之上限型股權連結保本模型之評價和風險測量。該文是擴展Brennan and Schwartz (1976)模型發展一個路徑依賴之上限型股權連結保本模型，並且提出一個比二元數模型更精確的封閉解。此外，也對七個時間序列進行股價波動度之精確檢定，得知AR-ARCH(1)模型對上限型股權連結保本票券而言，較其它時間序列模型，更能有效估計股價之波動度。 第二篇文章是外國資產的風險管理。目前在國內金融市場上，國外金融商品很多，大都以外幣計價，因此匯率風險是投資人不可忽視的因子。本文拓展Kupiec(1999)模型，將匯率風險加入模型中，使投資人更有效進行風險管理。 / This thesis studies valuation, hedge and risk management of capped equity-linked and principal-protected notes by means of the following essays: (1) Design, Valuation and Comparison of Capped Equity-linked and Principal-protected Notes (2) Valuation and Risk Measurement of Capped Equity-linked and Principal-protected Notes with Path Dependence (3) Risk Management of Foreign Assets Capped equity-linked and principal-protected notes are similar with barrier options. There exists delta jump as stock price or growth rate reaches the barrier. But previous studies about equity-linked and principal-protected notes with a restricted growth rate of stock price never explicitly discussed how the delta jump could be solved. In my first essay, I present a new design for capped equity-linked and principal-protected notes and add an adjustable factor to growth rate of stock price in such a way that the adjustable factor narrows the gap between the current stock growth rate and the capped stock growth rate and thus really reduces the magnitude of the delta jump and hence lowers the hedging cost for brokers. Recently, the focus of previous studies about principal-protected notes has been on either the restriction on the rate of stock return or the path dependence on the underlying asset, but not both in the same context. In my second essay, I develop a model on the capped, equity-linked and principal-protected notes with path dependence. There are two issues in this article. The first issue is valuation on the capped, equity-linked and principal-protected notes with path dependence. I find a closed-form approximation using the 2nd-order Taylor approximation and the method of Vorst (1992) that has higher accuracy than binomial tree model as maturity time or volatility becomes large. The second issue is risk measurement. I use VaR model to evaluate market risk of the principal-protected notes, and employ seven univariate time series models to forecast volatility and examine the accuracy. Additionally, investors may well encounter potential loss as the prices of financial products are reduced in the secondary market. The VaR is mainly concerned with the downside risk and becomes a standard measure of financial market risk that is increasingly used by investors. But if we want to apply 〝textbook〞formulation to risk management of foreign assets, there leaves exchange rate risk out of consideration. Therefore, I extend the work by Kupiec (1999) to present VaR formula with exchange rate risk for foreign assets and then to manage market risk usefully.

Nanotechnology is expected to play a major role in many technology areas including electronics, materials, and defense. One of the most popular tools for nanoscale surface analysis is the atomic force microscope (AFM). AFM can be used for surface manipulation along with surface imaging. The primary motivation for this research is to demonstrate AFM-based lithography on thin films using cantilevers with integrated heaters. These thermal cantilevers can control the temperature at the end of the tip, and hence they can be used for local in-situ thermal analysis. This research directly addresses applications like nanoscale electrical circuit fabrication/repair and thermal analysis of thin-films. In this study, an investigation was performed on two thin-film materials. One of them is co-polycarbonate, a variant of a polymer named polycarbonate, and the other is an energetic material called pentaerythritol tetranitrate (PETN). Experimental methods involved in the lithography process are discussed, and the results of lithographic experiments performed on co-polycarbonate and PETN are reported. Effects of dominant parameters during lithography experiments like time, temperature, and force are investigated. Results of simulation of the interface temperature between thermal cantilever tip and thin film surface, at the beginning of the lithography process, are also reported.

Η οπτική συνεκτική τομογραφία με τη χρήση συχνοτήτων ( FD-OCT) είναι μια ενδαγγειακή απεικονιστική μέθοδος που χρησιμοποιεί εγγύς στο υπέρυθρο φως, για να παράγει υψηλής ανάλυσης εικόνες του τοιχώματος του αυλού του αγγείου. Όπως και στην τεχνολογία υπερήχων, εκπέμπεται φωτεινή ενέργεια η οποία ανακλάται και εξασθενεί, σύμφωνα με την υφή του προσπιπτομένου ιστού. Το OCT μπορεί να απεικονίσει, με ανάλυση από 10 έως 20 μm, μικροδομές του αγγειακού τοιχώματος με εξαίσια λεπτομέρεια. Μέχρι σήμερα, η δυνατότητα εφαρμογής της μεθόδου είχε περιοριστεί σε μικρές αρτηρίες διαμέτρου έως 4mm και δεν είχε εφαρμοστεί in vivo στα αγγεία των κάτω άκρων, κάτωθεν του επιπέδου των βουβώνων. Σκοπός της παρούσας μελέτης είναι να αναφερθεί για παγκοσμίως πρώτη φορά η ασφάλεια και η σκοπιμότητα της απεικόνισης με Οπτική Συνεκτική Τομογραφία του αρτηριακού άξονα των κάτω άκρων , κάτωθεν του επιπέδου της βουβώνας ( μηροϊγνυακός άξονας και κνημιαία αγγεία), καθώς και οι σχετιζόμενες με το FD-OCT επιπλοκές. Επιπρόσθετα, να διερευνηθούν για πρώτη φορά, με τη χρήση FD-OCT, τα χαρακτηριστικά του αγγειακού τοιχώματος του ανωτέρω άξονα (τόσο πριν όσο και μετά από αγγειοπλαστική ή/και τοποθέτηση stent), η μορφολογία της αθηρωματικής πλάκας, η μορφολογία και η ποσοτικοποίηση της υπερπλασίας του νέου εσωτερικού χιτώνα (neointima) εντός του stent, η επαναστένωση εντός του stent (ISR) και η κακή εναπόθεση (malapposition) των stent struts σε μια σειρά από ασθενείς που πάσχουν από περιφερική αρτηριοπάθεια (PAD). Μελετήθηκαν, με ποσοτική ανάλυση του αυλού τους (Quantitative vascular analysis), αρτηρίες με διάμετρο έως 7 χιλιοστά. Μικτά χαρακτηριστικά από περιοχές πλούσιες σε λιπίδια, εναποθέσεις ασβεστίου και ασβεστοποιημένες πλάκες, νεκρωτικές περιοχές και ίνωση εντοπίστηκαν σε όλες τις απεικονιζόμενες αθηροσκληρωτικές βλάβες. Ωστόσο, με βάση το επικρατέστερο από τα παραπάνω απεικονιστικά χαρακτηριστικά, οι βλάβες στο πλαίσιο της έρευνας ταξινομήθηκαν ως αμιγώς ινωτικές, ως ινοασβεστοποιημένες, ως πλούσιες σε λιπίδια και τέλος ως νεκρωτικές/ασβεστοποιημένες. Συσσώρευση των μακροφάγων εντός της αθηρωματικής πλάκας σημειώθηκε σε μικρό ποσοστό των de novo αθηρωματικών αλλοιώσεων. Ποικίλοι βαθμοί υπερπλασίας του νέου έσω χιτώνα απεικονίσθηκαν σε όλες τις περιπτώσεις ISR αλλοιώσεων, με καθαρά ινωτικά χαρακτηριστικά και σημαντική νεοαγγείωση σε κάποιες από αυτές. Η νεοαγγείωση συνέπεσε με το επίπεδο της μέγιστης στένωσης του αγγειακού αυλού. Σημαντικού βαθμού διαχωρισμός με μεγάλο περιορισμό του αγγειακού αυλού, τέτοιος ώστε να απαιτηθεί να τοποθετηθεί ενδοαυλικό stent, ανιχνεύθηκε σε αρκετές περιπτώσεις της de novo αθηρωμάτωσης. Η ψηφιακή αφαιρετική αγγειογραφία παρέλειψε να προσδιορίσει μεγάλο ποσοστό των σοβαρών διαχωρισμών μετά από αγγειοπλαστική. Η νεοαθηροσκλήρυνση εντός του νέου έσω χιτώνα των κνημιαίων φαρμακευτικών stents (DES), είναι ένα συχνό εύρημα τόσο στους συμπτωματικούς όσο και στους ασυμπτωματικούς ασθενείς. Μπορούμε να υποθέσουμε ότι, κατά αναλογία με τα εμφυτευμένα DES στα στεφανιαία αγγεία, η ελαττωματική ενδοθηλιοποίηση που προκαλείται από την εκλυόμενη φαρμακευτική ουσία, μαζί με την νεοαγγείωση που αναπτύσσεται μεταξύ των stent struts, μπορούν να υποδαυλίσουν την νεοαθηροσκλήρυνση εντός του νέου έσω χιτώνα των κνημιαίων DES, η οποία μπορεί να οδηγήσει σε επαναστένωση εντός του stent (ISR) και απώλεια του εμβαδού του αυλού των περιφερικών αρτηριών. Οι παρατηρήσεις της μελέτης αυτής θέτουν σε αμφισβήτηση το παραδοσιακό τρόπο κατανόησης της περιφερειακής επαναστένωσης εντός του stent ως μιας απλής υπερπολλαπλασιαστικής απάντησης στο βαρότραυμα. Η απεικόνιση με FD-OCT είναι ένα βέλτιστο πειραματικό εργαλείο για την αξιολόγηση της εξέλιξης της αθηροσκληρωματικής νόσου και την επαναστένωση του αγγείου. Μπορεί να παρέχει υψηλής ευκρίνειας ενδοαγγειακή απεικόνιση κατά τη διάρκεια αγγειοπλαστικών επεμβάσεων στα κάτω άκρα και θα μπορούσε να αποδειχθεί κλινικά χρήσιμο για τον προσδιορισμό της εντός του stent πρόπτωσης ιστού και του strut malapposition. Παρ 'όλα αυτά, δεν πρέπει να χρησιμοποιηθεί ως εργαλείο για τη συνήθη κλινική πρακτική μέχρι να προκύψουν στοιχεία από περαιτέρω κλινικές δοκιμές για τον καθορισμό των ειδικών ενδείξεων της απεικόνισης με FD-OCT στις περιφερικές αρτηρίες. / Optical coherence tomography (OCT) is a catheter-based imaging method that employs near-infrared light to produce high-resolution intravascular images. OCT can readily visualize vessel microstructure at a 10- to 20-μm resolution with exquisite detail. To date, however, applicability of the method has been limited to small diameter arteries (≤4 mm). To the best of the author’s knowledge, this study is the first worldwide that demonstrates the safety and clinical feasibility of frequency domain Optical Coherence Tomography (FD-OCT) imaging of infrainguinal vessels in vivo during infrainguinal angioplasty procedures. It is also the first study that reports the use of intravascular FD-OCT to detect and characterize in-stent neointimal tissue following infrapopliteal drug eluting stent (DES) placement in patients suffering from critical limb ischemia. Quantitative lumen analysis of arteries with diameter up to 7 mm was performed. High-resolution OCT images provided exquisite two-dimensional axial and longitudinal views of the infrainguinal arteries and allowed thorough investigation of a variety of angioplasty sequela, including and not limited to intimal tears and dissection flaps, white and red thrombus, stent mesh malapposition, and intrastent plaque prolapse. Of interest, OCT identified cases of suboptimal postangioplasty outcome that single-plane subtraction angiography did not recognize and accounted. Mixed features of lipid pool areas, calcium deposits and calcified plaques, necrotic areas, and fibrosis were identified in all of the imaged atherosclerotic lesions. However, based on the predominant baseline imaging findings, lesions under investigation were classified as purely fibrotic, fibrocalcific, mostly lipid-laden and necrotic/calcified. Intraplaque accumulation of macrophages was noted in some of de novo atheromatic lesions. Varying degrees of neointimal hyperplasia were demonstrated in all cases of in stent restenosis (ISR) lesions with purely fibrotic features and considerable neovascularization in some of them. The latter finding coincided with the level of maximum vessel stenosis in all cases. Neoatherosclerosis following infrapopliteal DES placement is a frequent finding in both symptomatic and asymptomatic patients. Our preliminary observations allow us to speculate that analogous to coronary implanted DES, defective endothelialization induced by the eluted drug, along with neovascularization developing between the stent struts, may incite neointimal neoatherosclerosis, which may result in ISR and lumen loss of the peripheral arteries. It also seems that infrapopliteal neoatherosclerosis may be a significant contributing factor for ISR rather than a minor and sporadic process, highlighting the clinical significance of the phenomenon. Our observations put in dispute the traditional way of understanding peripheral in-stent restenosis as a simple hyperproliferative response to barotraumas and may explain the paramount importance of aggressive risk factor modification strategies. Neointimal neoatherosclerosis as identified by FD-OCT may have a role in the development of below-the-knee restenosis and thus warrants further investigation by larger controlled studies. Moreover, it may prove clinically useful for the determination of intrastent tissue prolapse and strut malapposition. FD-OCT should not be utilized as a tool for routine clinical practice until evidence from further clinical trials emerge to determine the specific indications for OCT imaging of the peripheral arteries.