Improvement of the 3ω\omega thermal conductivity measurement technique at nanoscale

The reduction of the thermal conductivity in nanostructures opens up the possibility of exploiting for thermoelectric purposes also materials such as silicon, which are cheap, available and sustainable but with a high thermal conductivity in their bulk form. The development of thermoelectric devices based on these innovative materials requires reliable techniques for the measurement of thermal conductivity on a nanometric scale. The approximations introduced by conventional techniques for thermal conductivity measurements can lead to unreliable results when applied to nanostructures, because heaters and temperature sensors needed for the measurement cannot have a negligible size, and therefore perturb the result. In this paper we focus on the 3$\omega$ technique, applied to the thermal conductivity measurement of suspended silicon nanomembranes. To overcome the approximations introduced by conventional analytical models used for the interpretation of the 3$\omega$ data, we propose to use a numerical solution, performed by means of finite element modeling, of the thermal and electrical transport equations. An excellent fit of the experimental data will be presented, discussed, and compared with an analytical model

Typing of Campylobacter jejuni and C. coli isolated from laying hens during the production cycle

C. jejuni and C. coli isolated on three layer farms during the production cycle were typed by PCR-RFLP flagellin gene profiling. Three typical restriction patterns were detected for C. coli (H, O, R), 5 for C. jejuni (I, P, Q, T, S) and 8 were common for both. The D profile was present in all three flocks. C fla-type was detected on farms A and B. The results of the study suggest that some genotypes tend to prevail and persist more than others on farms and in certain geographic areas

Occurrence of pathogenic and faecal Escherichia coli in layer hens

A total of 117 Escherichia coli from colibacillosis affected (APEC) and clinically healthy birds (AFEC) were serotyped and tested for the presence of virulence genes: iss, tsh, cva. A total of 54.5% E. Coli were typeable and 15 different serogroups were identified. The most common serogroups among APEC strains were O78, O2 and O128, whereas O139 was predominant in faecal strains from healthy birds. Iss, tsh e cva were more frequently detected among the septicaemic E. coli strains. The association of virulence genes was observed. Particularly, the pathotype iss-tsh-cva was present in 46.5% of APEC strains. Referring to serogroups, E. coli O78 and O2 originating from colibacillosis affected birds were always isstsh- cva positive but did not share virulence genes when they came from healthy birds

Avian Pathogenic Escherichia coli in Audouin gulls (Larus audouinii) Could they affect the surviving of the bird colonies

A total of 39 E. coli strains isolated from cloacal swabs and unhatched eggs of Audouin's gulls (Larus audouinii) living the Salento coast (Italy) were serotyped and molecular characterized for the presence of irp2, fyuA, tsh, papC, fimC, iucD, and eae genes described for Avian Pathogenic E. coli (APEC). Eight different serogroups (O1, 06, 08, 015, 075, 0139, 0146, 0147) were distinguished: we recorded a very high rate of untypeable strains. Genotyping by PCR achieved to detect fimC and irp2, described for APEC strains, as most predominant genes circulating in the gulls population, accounting for 94.87% and 97.43% respectively. Nevertheless, a significant co-existance of virulence genes was demonstrated to belong to E.coli of eggs origin. Particularly, fimC/tsh/iucD pathotype, recognized as most responsible of illness in poultry, emerged in 8.69% of E. coli of eggs origin

Interaction of glutathione transferase from horse erythrocytes with 7-chloro-4-nitrobenzo-2-oxa-1,3-diazole

7-Chloro-4-nitrobenzo-2-oxa-1,3-diazole reacts with two thiol groups of the dimeric horse erythrocyte glutathione transferase at pH 5.0, with strong inactivation reversible on dithiothreitol treatment. The inactivation kinetic follows a biphasic pattern, similar to that caused by other thiol reagents as recently reported. Both S-methylglutathione and 1-chloro-2,4-dinitrobenzene protect the enzyme from inactivation. Analysis of the reactive SH group-containing peptide gives the sequence Ala-Ser-Cys-Leu-Tyr, identical with that of the peptide that contains the reactive cysteine 47 of the human placental transferase. In the presence of glutathione, the enzyme is not inactivated by this reagent, but it catalyzes its conjugation to glutathione. At higher pH values, 7-chloro-4-nitrobenzo-2-oxa-1,3-diazole reacts with 2 tyrosines/dimer and lysines, as well as with cysteines. Reaction with lysine seems essentially without effect on activity; whether the reactive tyrosines are important for activity could not be determined using this reagent only. However, 2 tyrosines among the 4 that are nitrated by tetranitro-methane are important for activity

Selective organic functionalization of polycrystalline silicon-germanium for bioMEMS applications

AbstractWe selectively immobilized organofunctional silanes on top of polycrystalline silicon-germanium (poly-SiGe) layers, as a first step towards the fabrication of poly-SiGe-based bioMEMS (biomedical MicroElectroMechanicalSystems) by means of standard UV photolithography. 3-aminopropyl-dimethyl-ethoxysilane (APDMES) and 3-aminopropyl-triethoxysilane (APTES) molecules were immobilized onto resist-patterned poly-SiGe surfaces. The protocols for surface hydroxylation and silane immobilization were designed to be CMOS-compatible and to avoid damage to photoresist. Silanized surfaces were investigated both by means of fluorescence microscopy, and by FEG-SEM observation after labeling with 30 nm-diameter gold nanoparticles (NPs). We report the silanization protocols, together with the results indicating successful organic functionalization of the samples

Operation of an optoelectronic crossbar switch containing a terabit-per-second free-space optical interconnect

The experimental operation of a terabit-per-second scale optoelectronic connection to a silicon very-large-scale-integrated circuit is described. A demonstrator system, in the form of an optoelectronic crossbar switch, has been constructed as a technology test bed. The assembly and testing of the components making up the system, including a flip-chipped InGaAs-GaAs optical interface chip, are reported. Using optical inputs to the electronic switching chip, single-channel routing of data through the system at the design rate of 250 Mb/s (without internal fan-out) was achieved. With 4000 optical inputs, this corresponds to a potential aggregate data input of a terabit per second into the single 14.6 /spl times/ 15.6 mm CMOS chip. In addition 50-Mb/s data rates were switched utilizing the full internal optical fan-out included in the system to complete the required connectivity. This simultaneous input of data across the chip corresponds to an aggregate data input of 0.2 Tb/s. The experimental system also utilized optical distribution of clock signals across the CMOS chip