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Objective The aim of this study was to establish a triaging system for assessment of breast referrals from primary care to ensure safe and effective breast services without compromising breast cancer management. Background COVID-19 was officially declared a global pandemic on 11 March 2020, and with no effective treatment available, preventing spread has been paramount. Previously, all referrals from primary care were seen in the rapid-access breast clinic (RABC). Clinic appointments exposed patients and healthcare professionals to risk. Method Initial triage during the lockdown was in line with national governing body guidance, rejected low risk referrals and streamed remaining patients through a telephone consultation to RABC or discharge. A modified triage pathway streamed all patients through virtual triage to RABC, telephone clinic or discharge with advice and guidance categories. Demographics, reasons for referral and outcomes data were collected and presented as median with range and frequency with percentages. Results Initial triage (23 March–23 April 2020) found fewer referrals with a higher percentage of breast cancer diagnoses. Modified triage (22 June–17 July 2020) resulted in a 35.1% (99/282) reduction in RABC attendance. Overall cancer detection rate remained similar at 4.2% of all referrals pre-COVID (18/429) and 4.3% (12/282) during modified triage. After six months follow-up of patients not seen in RABC during the modified triage pathway, 18 patients were re-referred to RABC and none were diagnosed with cancer. Conclusion A modified triage pathway has the potential to improve triage efficiency and prevent unnecessary visits during the COVID-19 pandemic. Further refinement of pathway is feasible in collaboration with primary care.

Biting midges, Culicoides spp. (Diptera: Ceratopogonidae), are important vectors of viral pathogens. Following the outbreak of bluetongue serotype 8 in Europe between 2006 and 2009, many Culicoides surveillance programmes were initiated to identify vector-active periods, in accordance with European Commission regulation 2007/1266/EC. This study utilized surveillance data from 4 years of continuous light-trapping at 14 sites in Northern Ireland. The number of captured Culicoides varied from none during the vector-free period (December–April) to more than 36 000 per night during peak activity in the summer. The Obsoletus group represented 75% of Culicoides collected and the Pulicaris group represented 21%. A total of 91% of Culicoides were female, of which 42% were parous. Abundance data, sex ratios and parous rates suggested that both the Obsoletus and Pulicaris groups underwent three generations/year. The Obsoletus group was associated with cattle-rearing habitats and woodland, the Impunctatus group was found in habitats related to sheep rearing and the Pulicaris group were associated with both cattle and sheep. Housing did not reduce incursion of female Obsoletus group Culicoides but it did for males and for the Pulicaris group Culicoides. The influence of housing was strongly affected by time of year, probably reflecting the presence of livestock indoors/outdoors.

Biting midges (Culicoides spp.) are vectors of bluetongue and Schmallenberg viruses. Treatment of mesh barriers is a common method for preventing insect-vectored diseases and has been proposed as a means of limiting Culicoides ingression into buildings or livestock transporters. Assessments using animals are costly, logistically difficult and subject to ethical approval. Therefore, initial screening of test repellents/insecticides was made by applying treatments to mesh (2 mm) cages surrounding Onderstepoort light traps. Five commercial treatments were applied to cages as per manufacturers' application rates: control (water), bendiocarb, DEET/p-menthane-3,8-diol (PMD) repellent, Flygo (a terpenoid based repellent) and lambda-cyhalothrin. The experimental design was a 5 × 5 Latin square, replicated in time and repeated twice. Incongruously, the traps surrounded by DEET/PMD repellent-treated mesh caught three to four times more Obsoletus group Culicoides (the commonest midge group) than the other treatments. A proposed hypothesis is that Obsoletus group Culicoides are showing a dose response to DEET/PMD, being attracted at low concentrations and repelled at higher concentrations but that the strong light attraction from the Onderstepoort trap was sufficient to overcome close-range repellence. This study does not imply that DEET/PMD is an ineffective repellent for Culicoides midges in the presence of an animal but rather that caution should be applied to the interpretation of light trap bioassays.

Background: The World Health Organization (WHO) declared a novel coronavirus disease 2019 (COVID 19) pandemic on the 11 March 20 In response to this, the United Kingdom (UK) Association of Breast Surgeons (ABS) released guidelines on breast cancer management during the pandemic on the 15 March 20 The UK was in lockdown on the 23 March 20 Whilst the UK breast units adapted to deliver safe cancer services, many limited and some stopped all oncoplastic and reconstructive breast surgery (OPRBS) With careful stratification and prioritisation of cases, coupled with our existing successful integrated ambulatory day case surgery pathway, our unit continued to perform OPRBS safely and we present the outcomes of our OPRBS during the pandemic Materials and Methods: OPRBS performed between 11 March 20 and 31 July 20 were included in this study All OPRBS cases were supported by our multidisciplinary team Surgeons and patients followed hospital’s COVID 19 precautions policy Primary outcome measured was COVID 19 exposure before or after surgery Secondary outcomes measured were 30 days surgical complications and delay in adjuvant treatment Results: A total of 117 patients (120 breasts) had breast cancer related surgeries during the study period Ten patients (12 breasts), that is 10% underwent immediate OPRBS following breast conserving surgery or mastectomy were included in the study analysis All OPRBS were planned for ambulatory day case surgery (ADCS) Patients' age ranged was from 35 to 63 years There were 6 pre-pectoral implant based reconstructions, 4 partial breast reconstruction with chest wall perforator flaps, 1 therapeutic mammoplasty, and 1 central BCS with nipple reconstruction None contracted COVID 19 before or after surgery, 2 patient developed minor complications with no delay in adjuvant treatment Six patients were discharged on the day of surgery, and 4 patients were discharged within 23 hours of admission as part of our unit's integrated ADCS (

Mosquito-borne diseases resulting from the expansion of two key vectors, Aedes aegypti and Aedes albopictus (Diptera: Culicidae), continue to challenge whole regions and continents around the globe. In recent years there have been human cases of disease associated with Chikungunya, dengue and Zika viruses. In Europe, the expansion of Ae. albopictus has resulted in local transmission of Chikungunya and dengue viruses. This paper considers the risk that Ae. aegypti and Ae. albopictus represent for the U.K. and details the results of mosquito surveillance activities. Surveillance was conducted at 34 points of entry, 12 sites serving vehicular traffic and two sites of used tyre importers. The most common native mosquito recorded was Culex pipiens s.l. (Diptera: Culicidae). The invasive mosquito Ae. albopictus was detected on three occasions in southern England (September 2016, July 2017 and July 2018) and subsequent control strategies were conducted. These latest surveillance results demonstrate ongoing incursions of Ae. albopictus into the U.K. via ground vehicular traffic, which can be expected to continue and increase as populations in nearby countries expand, particularly in France, which is the main source of ex-continental traffic.

Raman imaging of diatomite nanoparticles uptake in cancer cells

Biting midges, Culicoides spp. (Diptera: Ceratopogonidae), are important vectors of viral pathogens. Following the outbreak of bluetongue serotype 8 in Europe between 2006 and 2009, many Culicoides surveillance programmes were initiated to identify vector-active periods, in accordance with European Commission regulation 2007/1266/EC. This study utilized surveillance data from 4 years of continuous light-trapping at 14 sites in Northern Ireland. The number of captured Culicoides varied from none during the vector-free period (December-April) to more than 36 000 per night during peak activity in the summer. The Obsoletus group represented 75% of Culicoides collected and the Pulicaris group represented 21%. A total of 91% of Culicoides were female, of which 42% were parous. Abundance data, sex ratios and parous rates suggested that both the Obsoletus and Pulicaris groups underwent three generations/year. The Obsoletus group was associated with cattle-rearing habitats and woodland, the Impunctatus group was found in habitats related to sheep rearing and the Pulicaris group were associated with both cattle and sheep. Housing did not reduce incursion of female Obsoletus group Culicoides but it did for males and for the Pulicaris group Culicoides. The influence of housing was strongly affected by time of year, probably reflecting the presence of livestock indoors/outdoors.

The use of porous silica nanoparticles (PSN) offers new perspectives in drug delivery and cancer therapy. PSN exhibit considerable potential for biological applications because of their biocompatibility, biodegradability and tunable porous nanostructure for drug delivery. Another advantage is the possibility to modify their external as well as internal surfaces. Nano-surface modification has proven to be beneficial for improving nanocarrier drug delivery and provides a wide range of functionalities. The aim of this study was to define the biocompatibility of the PSN and to settle a suitable experimental protocol to functionalize PSN.

The leaf oil of Heteropyxis dehniae Suess. (Heteropyxidaceae) was obtained by hydrodistillation and analyzed by GC/MS. The most abundant essential oil components are linalool (58.3%), 4-terpineol (9.8%), α-terpineol (3.6%), and caryophyllene oxide (3.1%). The antimicrobial activity against Bacillus cereus, Staphylococcus aureus, Pseudomonas aeruginosa, Escherichia coli, Candida albicans, and Aspergillus niger, and the in vitro cytotoxicity of the oil on PC-3, MDA-MB-231, Hs 578T, MCF7, SK-MEL-28, and 5637 human tumor cells were also examined. Caryophyllene oxide shows notable cytotoxic activity with LC50 values of 147–351 μM.

We have investigated the laser induced ablation–oxidation process on porous silicon layers having different porosities and thicknesses by non-destructive optical techniques. In particular, the interaction between a low power blue light laser and the porous silicon surfaces has been characterized by variable angle spectroscopic ellipsometry and Fourier transform infrared spectroscopy. The oxidation profiles etched on the porous samples can be tuned as functions of the layer porosity and laser fluence. Oxide stripes of width less than 2 µm and with thicknesses between 100 nm and 5 µm have been produced, depending on the porosity of the porous silicon, by using a 40 × focusing objective.

Background Although mucosal leishmaniasis is a prominent disease, it has been studied only to a limited extent. It is classically treated with parenteral antimony or, as a last resort, amphotericin B. Methods We treated Bolivian mucosal leishmaniasis due to Leishmania braziliensis with the oral agent miltefosine, 2.5 mg/kg/day for 28 days, and followed-up for 12 months. Results Seventy-two patients were evaluable. The cure rate for the 36 patients who had "mild" disease (i.e., affecting nasal skin and nasal mucosa) was 83%. The cure rate for the 36 patients who had more extensive disease (involving the palate, pharynx, and larynx) was 58%. Patients refused to be randomized to parenteral agents, but the cure rate for an almost contemporary group who was receiving amphotericin B (45 mg/kg over 90 days) was 7 (50%) of 14. Conclusions In this unrandomized trial, oral miltefosine was at least as effective as heroic doses of parenteral amphotericin B. The cure rate for miltefosine was approximately equivalent to historical cure rates using parenteral pentavalent antimony for mild and extensive disease in neighboring Peru. Although gastrointestinal side reactions do occur with miltefosine, its toxicity profile is superior to that of antimony and far superior to that of amphotericin B--in part because of the inherent attractiveness of oral versus parenteral agents. Our results suggest that miltefosine should be the treatment of choice for mucosal disease in North and South America.

The crude methanol bark extract of the Zimbabwean medicinal plant, Ozoroa insignis, showed in-vitro cytotoxic activity against Hep-G2 (human hepatocellular carcinoma), MDA-MB-231 (human mammary adenocarcinoma), and 5637 (human primary bladder carcinoma). Bioactivity-directed chromatographic separation led to isolation of anacardic acid and ginkgoic acid as the cytotoxic components.

Porous silicon biosensors are by far used in optical monitoring of molecular interactions. These photonic devices could greatly benefit of integration with specific microfluidic circuits that allow small volume, and thus low consumption of reagents, fast time of incubation, and highly controlled reaction conditions. In this paper, we summarize the experience of our research group in fabrication and characterization of optical biochip, and also present new, original results on biosensing. In particular, a porous silicon based microarray of one-dimensional photonic crystals has been integrated with innovative microfluidic circuit for parallel feeding of chemical solutions. The device has been used for the label free optical monitoring of ssDNA–cDNA interaction.

Gas and vapor sensing is an important task in the industrial field, both for production and safety, but this item is relevant also in social ground: from soil extraction to terrorism surveillance, there is always a volatile substance to be monitored and quantified. There are many transducing methods to detect gaseous substances and the most common is the so-called electrical nose: an array of gas sensitive semiconductors, such as ZnO, WO3, or other composite oxides, generates a current/voltage change on exposure to pure or mixed substances, and complex software analyzes the sensor response and quantifies the atmosphere composition. Even if it is a very diffuse and powerful device, the electronic nose and, in general, all the electrical gas sensors, suffers from several limitations. First, the oxide semiconductors are sensitive only at high temperature, so these devices are power consuming; moreover, the most severe limit is that electric power and high temperature cannot be used at all for monitoring explosive or flammable substances. From this point of view, optical sensors easily overcome these difficulties: light is contactless and can be generated with very low consumption (it is the case of light emitting diodes [LED]). In addition, optical sensors do not require electric contacts that may cause explosions or fire during sample preparation. Moreover, optical sensing can be remote, assuring total safety for instruments and operators. Therefore, in the presence of a harsh environment, optical sensing is by far the best technique for in situ monitoring of hazardous compounds.

Porous silicon (PS) based devices are nowadays under an intense and widespread investigation in the optoelectronic and sensing fields. Recently, the range of possible applications has been widened by the use of the liquid crystals (LCs), which can be infiltrated in the PS sponge-like structure. The large changes of the optical properties, as exhibited by LCs under the action of electrical or thermal fields, allow developing a new family of optical devices like tunable PS based multilayer mirrors, microcavities and optical filters. In this work, we have optically characterized the LC-PS heterogeneous composite as a guest-host system by means of the variable angle spectroscopic ellipsometry (VASE). A PS layer, 450nm thick, has been infiltrated with the nematic LC 5CB, and the main optical parameters, anisotropic refractive indices and thickness of both materials, have been estimated below and above the isotropic transition temperature, at 27.0 degrees C and 38.0 degrees C respectively. We have found a clear indication that the LC molecules tend to align parallel to the direction of the pore columns.

Nanostructured materials, due to their peculiar physical and chemical properties, constitute the new class of functional supports for specific innovative applications. There is a strong competition between synthetic, man-made nanostructured materials and those coming directly from nature: the first ones can be precisely tailored by properly design and fabrication; the second ones are directly available without any cost of production. In this paper, we report our latest achievements on different materials, porous silicon, zinc oxide nanowires and diatomite powders, which belong to these categories.

Diatomite is a natural fossil material of sedimentary origin, composed by fragments of diatom siliceous skeletons. Due to its chemical inertness, thermal stability, high surface area, non-toxicity and biocompatibility, diatomite is considered an ideal material for the preparation of diatomite silica drug delivery nanocarriers. In this work, the properties of diatomite nanoparticles (DNPs) as potential system for drug delivery in cancer cells were exploited.

In this preliminary work, we report about porous silicon (PSi) non-symmetric optical microcavities as transducers modified by organic molecular beam deposition (OMBD) of N,N?????????-1H,1H-perfluorobutyldicyanoperylene- carboxydi-imide (PDIF-CN2), an electrically conductive organic material. PSi is a very effective optical transducer, due to its sponge-like morphology, but not a very good electrical one. Joule evaporation of PDIF-CN2 could improve electrical conductivity of PSi transducer, making the device a dual signal sensor. ?????? 2014 AEIT.

An optical model for Raman response of thin metal films has been developed, taking into account attenuation effects and multi-reflections occurring at film edges. Film thickness and surface morphology of nanometer thin NbN films have been inferred in the framework of this model using micro-Raman measurements. Results have been compared with those obtained by means of spectroscopic ellipsometry. The absolute value of the thickness is determined with a precision better than 20% on nanometric scale allowing us to control surface morphology with high accuracy also on large areas.

Interfaces play a key role in optical biosensor fabrication: biological molecules need to be integrated with inorganic transducers, both electrical and optical, preserving their functions and specificity. Single DNA stands, proteins, enzymes, and antibodies must be blocked on surface by absorption or covalently, depending on different chemistry used. In case of proteins and antibodies, also orientation of biological molecules is very important. In this work, we present our results on a biological passivation procedure that employs hydophobins, small amphiphilic proteins. Since these proteins complex with sugars in nature, we also suggest their utilization as functional layer in optical biosensor for glucose.

One of the most important goals in the fields of biology and medicine is the possibility to dispose of efficient tools for the characterization of the extraordinary complexity of ligand-receptor interactions. To approach this theme, we explored the use of crystalline silicon (cSi) technology for the realization of a biotechnological device in which the ligand-receptor interactions are revealed by means of optical measurements. Here, we describe a chemical procedure for the functionalization of microwell etched on silicon wafers, and the subsequent anchoring of biological molecules like an antibody anti-A20 murine lymphoma cell line. The optical analysis of the interaction on the biochips between the bound biomolecule and their corresponding ligand indicated that the functionalized cSi is suitable for this application.

In this work, we have fabricated a porous silicon (PSi) Bragg reflectors microarray using a proper technological process based on photolithography and electrochemical anodization of silicon. Each element of the array is characterized by a diameter of 200 μm. The PSi structures have been used as platform to immobilize label-free DNA probe and a simple optical method has been employed to investigate the interaction between probe-DNA and its complementary target. In order to confirm the specificity of the DNA hybridization, we have also verified that the reaction of probe-DNA with non-complementary DNA did not occur.

Valves of Coscinodiscus wailesii diatoms, monocellular micro-algae characterized by a diameter between 100 and 200 μm, show regular pores patterns which confine light in a spot of few μm2. This effect can be ascribed to the superposition of diffracted wave fronts coming from the pores on the valve surface. We studied the transmission of partially coherent light, at different wavelengths, through single valves of Coscinodiscus wailesii diatoms. The spatial distribution of transmitted light strongly depends on the wavelength of the incident radiation. Numerical simulations help to demonstrate how this effect is not present in the ultraviolet region of the light spectrum, showing one of the possible evolutionary advantages represented by the regular pores patterns of the valves. Valves of Coscinodiscus wailesii diatoms, monocellular micro-algae characterized by a diameter between 100 and 200 mu m, show regular pores patterns which confine light in a spot of few mu m(2). This effect can be ascribed to the superposition of diffracted wave fronts coming from the pores on the valve surface. We studied the transmission of partially coherent light, at different wavelengths, through single valves of Coscinodiscus wailesii diatoms. The spatial distribution of transmitted light strongly depends on the wavelength of the incident radiation. Numerical simulations help to demonstrate how this effect is not present in the ultraviolet region of the light spectrum, showing one of the possible evolutionary advantages represented by the regular pores patterns of the valves.

In this work, we report on the fabrication of an hybrid material based on a porous silicon (PSi) layer infiltrated by an amino functionalized poly(e-caprolattone) (PCL-NH2). The organic–inorganic structure has been characterized by variable angle spectroscopic ellipsometry, optical reflectometry and water contact angle measurements. A polymer coated PSi layer, 3 μm thick, shows improved wettability and chemical stability against long lasting, up to 18 min, exposure to an alkaline environment. Even after basic treatment, the structure still retains a very good quality optical response, so that it may be proposed as a high performance platform for biochemical sensing applications.

Diatoms are monocellular micro-algae provided with external valves, the frustules, made of amorphous hydrated silica. Frustules present patterns of regular arrays of holes, the areolae, characterized by sub-micrometric dimensions. Frustules from centric diatoms are characterized by a radial disposition of areolae and exhibit several optical properties, such as photoluminescence, lens-like behavior and, in general, photonic-crystal-like behavior as long as confinement of electromagnetic field is concerned. In particular, intrinsic photoluminescence from frustules is strongly influenced by the surrounding atmosphere: on exposure to gases, the induced luminescence changes both in the optical intensity and peaks positions. To give specificity against a target analyte, a key feature for an optical sensor, a biomolecular probe, which naturally recognizes its ligand, can be covalently linked to the diatom surface. We explored the photoluminescence emission properties of frustules of Coscinodiscus wailesii centric species, characterized by a diameter of about 100-200 μm, on exposure to different vapours and in presence of specific bioprobes interacting with target analytes. Very high sensitivities have been observed due to the characteristic morphology of diatoms shells. Particular attention has been devoted to the emission properties of single frustules. Diatoms are monocellular micro-algae provided with external valves, the frustules, made of amorphous hydrated silica. Frustules present patterns of regular arrays of holes, the areolae, characterized by sub-micrometric dimensions. Frustules from centric diatoms are characterized by a radial disposition of areolae and exhibit several optical properties, such as photoluminescence, lens-like behavior and, in general, photonic-crystal-like behavior as long as confinement of electromagnetic field is concerned. In particular, intrinsic photoluminescence from frustules is strongly influenced by the surrounding atmosphere: on exposure to gases, the induced luminescence changes both in the optical intensity and peaks positions. To give specificity against a target analyte, a key feature for an optical sensor, a biomolecular probe, which naturally recognizes its ligand, can be covalently linked to the diatom surface.We explored the photoluminescence emission properties of frustules of Coscinodiscus wailesii centric species, characterized by a diameter of about 100-200 mu m, on exposure to different vapours and in presence of specific bioprobes interacting with target analytes. Very high sensitivities have been observed due to the characteristic morphology of diatoms shells. Particular attention has been devoted to the emission properties of single frustules.

Several biological organisms, from some sea shells to butterflies, exhibit sophisticated optical systems, which have been developed during the evolution of each species. The diatoms are microscopic algae enclosed between two valves of hydrated amorphous silica. These intricate structures, called frustules, show quite symmetric patterns of micrometric and nanometric pores. Their strong similarity with man-made objects suggests to exploit the optical properties of the frustules in light guiding and optical transducing. We have found very interesting results, both from the experimental and numerical points of view. Several biological organisms, from some sea shells to butterflies, exhibit sophisticated optical systems, which have been developed during the evolution of each species. The diatoms are microscopic algae enclosed between two valves of hydrated amorphous silica. These intricate structures, called frustules, show quite symmetric patterns of micrometric and nanometric pores. Their strong similarity with man-made objects suggests to exploit the optical properties of the frustules in light guiding and optical transducing. We have found very interesting results, both from the experimental and numerical points of view. © 2008 Elsevier Ltd. All rights reserved.

Diatoms are monocellular micro-algae provided with external valves, the frustules, made of amorphous hydrated silica. Frustules present patterns of regular arrays of holes, the areolae, characterized by sub-micrometric dimensions. In particular, frustules from centric diatoms are characterized by a radial disposition of areolae and exhibit several optical properties, such as photoluminescence variations in presence of organic vapors and photonic-crystal-like behaviour as long as propagation of electromagnetic field is concerned. We have studied the transmission of coherent light, at different wavelengths, through single frustules of Coscinodiscus Walesii diatoms, a centric species characterized by a diameter of about 150 μm. The frustules showed the ability to focalize the light in a spot of a few μm2, the focal length depending on the wavelength of the incident radiation. This focusing effect takes place at the centre of the frustule, where no areolae are present and, as it is confirmed by numerical simulations, it is probably due to coherent superposition of unfocused wave fronts coming from the surrounding areolae. Diatoms-based micro-lenses could be used in the production of lensed optical fibers without modifying the glass core and, in general, they could be exploited with success in most of the optical micro-arrays. Diatoms are monocellular micro-algae provided with external valves, the frustules, made of amorphous hydrated silica. Frustules present patterns of regular arrays of holes, the areolae, characterized by sub-micrometric dimensions. In particular, frustules from centric diatoms are characterized by a radial disposition of areolae and exhibit several optical properties, such as photoluminescence variations in presence of organic vapors and photonic-crystal-like behaviour as long as propagation of electromagnetic field is concerned. We have studied the transmission of coherent light, at different wavelengths, through single frustules of Coscinodiscus Walesii diatoms, a centric species characterized by a diameter of about 150 urn. The frustules showed the ability to focalize the light in a spot of a few μm2, the focal length depending on the wavelength of the incident radiation. This focusing effect takes place at the centre of the frustule, where no areolae are present and, as it is confirmed by numerical simulations, it is probably due to coherent superposition of unfocused wave fronts coming from the surrounding areolae. Diatoms-based micro-lenses could be used in the production of lensed optical fibers without modifying the glass core and, in general, they could be exploited with success in most of the optical micro-arrays.

The development of label-free optical biosensors could have a great impact on life sciences as well as on screening techniques for medical and environmental applications. Peptide nucleic acid (PNA) is a nucleic acid analog in which the sugar phosphate backbone of natural nucleic acid has been replaced by a synthetic peptide backbone, resulting in an achiral and uncharged mimic. Due to the uncharged nature of PNA, PNA-DNA duplexes show a better thermal stability respect the DNA-DNA equivalents. In this work, we used an optical biosensor, based on the porous silicon (PSi) nanotechnology, to detect PNA-DNA interactions. PSi optical sensors are based on changes of reflectivity spectrum when they are exposed to the target analytes. The porous silicon surface was chemically modified to covalently link the PNA which acts as a very specific probe for its ligand ( c DNA).

In this work, we report on the light focusing ability exploited by the microshell of a marine organism: the Coscinodiscus wailesii diatom. A 100 μm spot size of a red laser beam is narrowed up to less than 10 μm at a distance of 104 μm after the transmission through the regular geometry of the diatom structure, which thus acts as a microlens. Numerical simulations of the electromagnetic field propagation show a good qualitative agreement with the experimental results. The focusing effect is due to the superposition of the waves scattered by the holes present on the surface of the diatom valve. Very interesting applications in micro-optic devices are feasible due to the morphological and biological characteristic of these unicellular organisms. © 2007 Optical Society of America.

Dielectric aperiodic Thue-Morse structures up to 128 layers have been fabricated by using porous silicon technology. The photonic band gap properties of Thue-Morse multilayers have been theoretically investigated by means of the transfer matrix method and the integrated density of states. The theoretical approach has been compared and discussed with the reflectivity measurements at variable angles for both the transverse electric and transverse magnetic polarizations of light. The photonic band gap regions, wide 70 nm and 90 nm, included between 0 and 30 degrees , have been observed for the sixth and seventh orders, respectively.

We have fabricated a microarray of porous silicon Bragg reflectors on a crystalline silicon substrate using a technological process based on standard photolithography and electrochemical anodization of the silicon. The array density is of 170 elements/cm(2) and each element has a diameter of 200 mu m. The porous silicon structures have been used as platform to immobilize an amino terminated DNA single strand probe. All fabrication steps have been monitored by spectroscopic reflectometry, optical and electron microscopy, and Fourier transform infrared spectroscopy. A label-free detection method has been employed to investigate the hybridization between micromolar DNA probe and its complementary target. Due to fast and low cost production, good reproducibility, and high quality optical features, this platform could be adopted also for other different microarray applications such as proteomics and medical diagnostics.