Effect of crystallization on morphology-conductivity relationship in polypyrrole/poly(?-caprolactone) blends

Electrically conducting blends, based on polypyrrole (PPy) as the conductive polymer and poly(?-caprolactone) (PCL) as an insulating polymeric matrix, were prepared by polymerizing pyrrole (Py) in its vapor state inside the PCL matrix. The roles of specific interactions between blend components as well as the crystallization of PCL matrix in the resulting morphology have been analyzed by Fourier-transform infrared spectroscopy (FTIR), thermo-optical analysis (TOA) and atomic force microscopy (AFM). The results indicate that PPy is located within both the intra and interspherulitic regions of the PCL matrix achieving a well-developed connected network. Compared with amorphous matrices, considerable conductivity (around 1 S/cm) was raised with the crystalline PCL matrix with only a relatively low level of the conductive polymer (∼5%) in the blend.     

Thermal deformation of loaded concrete at low temperatures. 3: Lightweight concrete

Longitudinal and transverse thermal deformation has been measured on lightweight concrete cylinders during a thermal cycle, from room temperature up to −90°C. Oven-dry samples show an almost linear, isotropic, reversible and load independent dilatational behaviour. Water-saturated samples behave in a different way; when load-free, thermal deformation is nearly isotropic, although highly non linear (between −10°C and −60°C) and ending with an irreversible expansion. When axially loaded (10 MPa), lightweight concrete shows a strongly anisotropic behaviour. Volumetric thermal deformation, for a given moisture content, does not seems to depend on applied load.     

Single-mode—multimode—single-mode and lossy mode resonance-based devices: a comparative study for sensing applications

In this work, a thin-film consisting of 15 bilayers (estimated thickness: 210 nm) of titanium (IV) oxide and poly(sodium 4-styrenesulfonate) is simultaneously deposited onto two optical fiber structures: a single-mode—multimode—single-mode (SMS) device and a lossy mode resonance (LMR)-based device. The performance of both structures, as refractometers and relative humidity sensors, is studied and compared. In both cases, the sensitivity of the LMR-based device (955 nm/RIU and 3.54 nm/RH %, respectively) highly improves the one of the SMS (142 nm/RIU and 0.3 nm/RH %). These facts can be taken into account when developing sensors based on either SMS or LMR technologies.     

Keynotes on bridges in Spain since the mid‐1980's

Spanish bridge engineering has developed creative and efficient answers to the challenges set by the extraordinary development of road and railway infrastructure during the last 25 years. This process provides continuity to the great tradition of good bridge engineering practice based on the ambition of overcoming such engineering challenges. These efforts also resulted in the exploration of new fields: typology, by generating new ideas to improve structural behavior; construction methods, by using new technologies (many of them perfected for other fields of activity) and by innovations using new specific methods for particular cases; structural materials by exploring the benefits of their new possibilities, deepening in the use of traditional composite steel‐concrete structures and starting a very interesting process of using composite materials. Consistent with the old aphorism “learning by doing” the lessons learnt from these daring tasks and experiences will remain in the back of these engineers' minds which will ensure continuity for future developments. At the present and in the near future, Spanish bridge engineering must face new challenges in design and construction in foreign countries, taking advantage of the experience gained during the past 25 years. Erfahrungen im Brückenbau in Spanien seit 1985 Brückenbauingenieure in Spanien haben sich mit ihren kreativen und wirtschaftlichen Lösungen den Herausforderungen der letzten 25 Jahre beim Ausbau der dortigen Straßenund Eisenbahnnetze gestellt. Diese Entwicklung steht in der langen und großen Tradition hervorragenden Brückenbaus, um solche Aufgaben zu meistern. In dieser Zeit wurde viel Neues entwickelt: Neue Typologien wurden erarbeitet, um die Tragwirkung zu verbessern; neue Technologien (viele davon für andere Aufgaben geschaffen) wurden adaptiert oder neue innovative Bauverfahren für spezifische Projekte kreiert; die Anwendung von Baustoffen wurde weiterentwickelt, resultierend z. B. in der verstärkten Nutzung von Stahl‐Verbundkonstruktionen, oder neue Verbundwerkstoffe wurden erstmals im Brückenbau eingesetzt. Im Sinne von “learning by doing” werden die Lehren und Erfahrungen dieser Aufgaben im Hinterkopf der Ingenieure bleiben und damit die Kontinuität für zukünftige Entwicklungen garantieren. Im Moment und in naher Zukunft müssen sich spanische Brückenbauingenieure den neuen Herausforderungen beim Entwurf und Bau von Brücken vor allem im Ausland stellen, wobei sie die Erfahrung der letzten 25 Jahren nutzen werden.     

Two-Layer Nanocoatings in Long-Period Fiber Gratings for Improved Sensitivity of Humidity Sensors

A relative humidity sensor based on the deposition of electrostatic self-assembled alumina ( $hbox{Al}_{2}hbox{O}_{3}$) and poly(sodium 4-styrenesulfonate) on the cladding of a long-period fiber grating (LPFG) has been designed. The sensitive material has a lower refractive index than that of the fiber cladding, which limits the sensitivity of the LPFG response. In order to enhance its sensitivity, a previous high refractive index coating has been deposited. The overlay thickness is of the order of magnitude of the light wavelength used to interrogate the sensor. A theoretical model of multilayer cylindrical waveguides based on coupled-mode theory has been used to predict the phenomenon. Experimentally, an increased wavelength shift of the attenuation bands (75%) was obtained during the fabrication of the sensor, and, what is more important, the sensitivity was improved by a ratio of almost four. The proposed method improves the performance of LPFG-based sensors characterized by overlays of low refractive index.      

An antibacterial submicron fiber mat with in situ synthesized silver nanoparticles

This work presents an alternative approach for fabricating electrospun submicron highly hydrophilic fiber mats loaded with silver nanoparticles. These fiber mats show a high efficient antibacterial behavior, very attractive for applications like wound healing and skin regeneration processes. The fabrication method is divided in two steps. First, poly(acrylic acid) (PAA) and β‐cyclodextrin (β‐CD) submicron fibers were electrospun and further stabilized using a thermal treatment, yielding stable hydrogel‐like fibers with diameters ranging from 100 nm up to several microns. In the second step, silver ions were loaded into the fibers and then reduced to silver nanoparticles in‐situ. The electrospinning parameters were adjusted to achieve the desired properties of the fiber mat (density, size) and afterwards, the characteristics of the silver nanoparticles (amount, size, aggregation) were tuned by controlling the silver ion loading mechanism. Highly biocide surfaces were achieved showing more than 99.99% of killing efficiency. The two‐step process improves the reproducibility and tunability of the fiber mats. To our knowledge, this is the first time that stable hydrogel fibers with a highly biocide behavior have been fabricated using electrospinning. © 2012 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Optical Fiber Humidity Sensors Using Nanostructured Coatings of SiO$_{2}$ Nanoparticles

In this paper, a new optical fiber humidity sensor based on superhydrophilic coating is proposed. The electrostatic self-assembly technique has been used to create a nanometric scale surface on the tip of a standard single-mode pigtail. The fabricated sensor has demonstrated a good linearity in the range from 40% to 98% of relative humidity (RH). A variation of 10 dB in reflected optical power is achieved with a response time of only 150 ms. Among other applications, this sensor is intended to be used for monitoring the human breathing, so high dynamic performances are required, specially in the higher RH ranges.     

Nanofilms on hollow core fiber-based structures: an optical study

The optical characteristics of one multimode fiber (MMF)-hollow core fiber (HCF)-structure when a nanofilm is deposited on it has been theoretically and experimentally studied. The electrostatic self-assembly method has been used as the deposition technique, and the polymers chosen are polydiallyldimethylammonium and Poly R-478. Two different types of HCF have been used for the fabrication of the devices: 10/150 and 50/150 /spl mu/m inner and outer diameters, respectively. Depending on several design parameters, the transmitted optical-power characteristic of the device experiences important changes that could be interesting towards development of several practical optical devices. The length and thickness of the HCF segment, the refractive index of the material deposited, the angle of the light when it reach the HCF section, and the wavelength of the light source will be analyzed.     

Allergic reactions to betalactams: studies in a group of patients allergic to penicillin and evaluation of cross-reactivity with cephalosporin

A group of 34 penicillin-allergic patients was studied to determine skin test reactivity to the different penicillins involved in inducing the allergic reaction and the cross-reactivity with side-chain-related and side-chain-unrelated cephalosporins. All the subjects selected for the study had to be skin test positive to at least one of the following determinants: benzyl-penicilloyl-polylysine (BPO-PLL), minor-determinant mixture (MDM), amoxicillin (AX), or ampicillin (AMP), or to possess in vitro IgE to the following conjugates: benzyl-penicilloyl-human-serum albumin (BPO-HSA), ampicilloyl-human-serum albumin (AMP-HSA), and amoxicilloyl-human-serum albumin (AX-HSA). Cephalexin (CE) and ceftazidime (CEF) were used to assess cross-reactivity. If skin tests to any of these compounds were positive, the patient was considered to be allergic; if negative, a challenge test was performed. Sixteen patients (47%) were skin test positive to BPO and/or MDM, and nine (26%) exclusively to AX and/or AMP. In three cases (8%), the RAST was positive although the skin test was negative; one to BPO-HSA and two to AX-HSA and AMP-HSA. Six patients (17%) needed to be challenged with the penicillin involved to establish the diagnosis. In five patients (14%), the skin tests were positive to CE and in none to CEF. In all the others, the skin tests were negative to both cephalosporins, and the patients tolerated the drugs when challenged. These results indicate the relevance of side-chain-specific minor determinants in betalactams allergy and provide support for the role of this chemical structure in the evaluation of cross-reactivity between penicillins and cephalosporins.     

Nanopatterned UV curable hydrogels for biomedical applications

With an increasing use of emerging patterning technologies such as UV-NIL in biotechnological applications there is at the same time a raising demand for new material for such applications. Here we present a PEG based precursor mixed with a photoinitiator to make it UV sensitive as a new material aimed at biotechnological applications. Using HSQ patterned quartz stamps we observed excellent pattern replication indicating good flow properties of the resist. We were able to obtain imprints with <20 nm residual layer. The PEG based resist has hydrogel properties and it swelling in water was observed by AFM.