Analysis of ISE in dynamic hardness measurements of β-Sn single crystals using a depth-sensing indentation technique

The dynamic indentation tests on (001) plane β-Sn single crystals having different growth directions under different peak indentation test load (10, 20, 30, 40, and 50 mN) has been investigated. The experimental results reveal that the measured hardness values exhibit a peak-load dependence, i.e., indentation size effect (ISE). Such peak-load dependence is then analyzed using the Meyer's law, the Hays–Kendall's approach, the Elastic/Plastic Deformation model, the Proportional Specimen Resistance (PSR) model, and the Modified PSR (MPSR) model. As a result, Modified PSR model is found to be the most effective for dynamic hardness determination of β-Sn single crystals.     

A site-isolated mononuclear iridium complex catalyst supported on MgO: Characterization by spectroscopy and aberration-corrected scanning transmission electron microscopy

Supported mononuclear iridium complexes with ethene ligands were prepared by the reaction of Ir(C₂H₄)₂(acac) (acac is CH₃COCHCOCH₃) with highly dehydroxylated MgO. Characterization of the supported species by extended X-ray absorption fine structure (EXAFS) and infrared (IR) spectroscopies showed that the resultant supported organometallic species were Ir(C₂H₄)₂, formed by the dissociation of the acac ligand from Ir(C₂H₄)₂(acac) and bonding of the Ir(C₂H₄)₂ species to the MgO surface. Direct evidence of the site-isolation of these mononuclear complexes was obtained by aberration-corrected scanning transmission electron microscopy (STEM); the images demonstrate the presence of the iridium complexes in the absence of any clusters. When the iridium complexes were probed with CO, the resulting IR spectra demonstrated the formation of Ir(CO)₂ complexes on the MgO surface. The breadth of the ν_CO bands demonstrates a substantial variation in the metal–support bonding, consistent with the heterogeneity of the MgO surface; the STEM images are not sufficient to characterize this heterogeneity. The supported iridium complexes catalyzed ethene hydrogenation at room temperature and atmospheric pressure in a flow reactor, and EXAFS spectra indicated that the mononuclear iridium species remained intact. STEM images of the used catalyst confirmed that almost all of the iridium complexes remained intact, but this method was sensitive enough to detect a small degree of aggregation of the iridium on the support.     

The effects of different greenhouse covering materials on energy requirement,growth and yield of aubergine

Effects of UV stabilised polyethylene (UV+PE), IR absorbers polyethylene (IR+PE), double layers of polyethylene (D-Poly) and single layer of polyethylene (PE), as greenhouse covers, on aubergine growth, productivity and energy requirement were investigated in a late autumn season (2001). The late and final yields of plants grown in D-Poly houses were higher than those grown in UV+PE, IR+PE and PE. Light transmission was the highest in PE, intermediate in UV+PE and IR+PE, and the lowest in D-Poly houses. Relative humidity was the highest in D-Poly, intermediate in IR+PE and UV+PE, and the lowest in PE houses. The plants in D-Poly houses grew and developed faster (more leaves and flowers) than those in IR+PE, UV+PE and PE houses. Plant growth and development in UV+PE and IR+PE houses was similar. Economic analyses showed that aubergine production was economically viable in D-Poly, UV+PE and IR+PE houses. For aubergine production in climatic conditions similar to Black Sea Region, the D-Poly greenhouse is strongly recommended, because there was a higher productivity and a lower heating requirement in comparison to UV+PE, IR+PE and PE houses.     

Study of Physically Transient Insulating Materials as a Potential Platform for Transient Electronics and Bioelectronics

Controlled degradation and transiency of materials is of significant importance in the design and fabrication of degradable and transient biomedical and electronic devices and platforms. Here, the synthesis of programmable biodegradable and transient insulating polymer films is reported, which have sufficient physical and chemical properties to be used as substrates for the construction of transient electronics. The composite structure can be used as a means to control the dissolution and transiency rate of the polymer composite film. Experimental and computational studies demonstrate that the addition of gelatin or sucrose to a PVA polymer matrix can be used as a means to program and either slow or enhance the transiency of the composite. The dissolution of the polymer composites are fitted with inverse exponential functions of different time constants; the lower time constants are an indication of faster transiency of the polymer composite. The addition of gelatin results in larger time constants, whereas the addition of sucrose generally results in smaller time constants.     

Science and technology policy in Turkey. National strategies for innovation and change during the 1983-2003 period and beyond

Summary An evaluation of Turkey's science and technology (S & T) policy in the last two decades has been made by using various indicators of S & T and technological innovation. National trends in inputs for research and development (R & D) activities, publication output and patent data have been studied for the implications of the S & T policy from 1983 to 2003. Some of the findings on the outcomes of policy measures in terms of inputs to R & D and publication output are as follows: (1) Total R & D expenditure, as percent of gross domestic product (GDP), increased from 0.32% in 1990 to 0.67% in 2002, (2) the fraction of R & D in the total expenditure for technological innovation increased from 6.6% in 1995-1997 to 29.2% in 1998-2000, and (3) the number of papers in the journals covered in the Science Citation Index (SCI) of the Institute for Scientific Information (ISI) increased from 464 in 1983 to 12160 in 2003 - a more than 26-fold increase in the last two decades.     

Synthesis, characterization and electrochromic properties of a conducting copolymer of pyrrole functionalized polystyrene with pyrrole

A well-defined polystyrene (PSt) based polymer containing at one end-chain 3,5-dibromobenzene moiety, prepared by atom transfer radical polymerization (ATRP), was modified in two reaction steps. First one constitutes a Suzuki coupling reaction between aromatic dibromine functional polymer and 3-aminophenylboronic acid, when a diamino-containing intermediate was obtained. The second step is a condensation reaction between the diamino functional polystyrene and 2-pyrrole aldehyde. Thus, a polymer containing a conjugated sequence having pyrollyl groups at the extremities was synthesized. The presence of oxidable pyrrole groups in the structure of the polymer permitted further electropolymerization. The structures of intermediate polymers were analyzed by spectral methods (¹H NMR, FTIR). Electrochemical copolymerization of pyrrole functionalized polymer (PStPy) with pyrrole was carried out in acetonitrile (ACN)-tetrabutylammonium tetrafluoroborate (TBAFB) solvent electrolyte couple. Characterization of the resulting copolymer were performed via Fourier transform infrared spectroscopy (FTIR), differential scanning calorimetry (DSC), scanning electron microscopy (SEM), spectroelectrochemical analysis, and kinetic study. Spectroelectrochemical analysis show that the copolymer of PStPy with Py has an electronic band gap (due to π-π* transition) of 2.4 eV at 393 nm, with a yellow color in the fully reduced form and a blue color in the fully oxidized form. Via kinetic studies, the optical contrast %ΔT was found to be 20% for P(PStPy-co-Py). Results showed that the time required to reach 95% of the ultimate T was 1.7 s for the P(PStPy-co-Py).     

An ATM queue manager handling multiple delay and loss priorities

The asynchronous transfer mode (ATM) technique has been widely accepted as a flexible and effective scheme to transport various traffic over the future broadband network. To fully utilize network resources while still providing satisfactory quality of service (QOS) to all network users, prioritizing the user's traffic according to their service requirements becomes necessary. During call setup or service provisioning, each service can be assigned a service class determined by a delay priority and a loss priority. A queue manager in ATM network nodes will schedule ATM cells departing and discarding sequence based on their delay and loss priorities. Most queue management schemes proposed so far only consider either one of these two priority types. The queue manager handles multiple delay and loss priorities simultaneously. Moreover, a cell discarding strategy, called push-out, that allows the buffer to be completely shared by all service classes, has been adopted in the queue manager. We propose a practical architecture to implement the queue manager by using available VLSI sequencer chips     

Residual and recurrent shunts after implantation of Cook detachable duct occlusion coils

Cough and chest wall pain at high altitude have only received passing mention in the medical literature. Increased minute ventilation of cold dry air at very high altitude is likely to cause airway irritation. This in turn may result in airway drying, mucus production, postnasal drip from vasomotor rhinitis, and bronchospasm acting individually or in combination to stimulate the vagal cough reflex. The cough is exacerbated further at extreme altitudes above 5500 m, and may result in intercostal muscle strain and single or multiple rib fractures. We present a case of multiple cough induced stress fractures and arthropathy documented by technetium-99 bone scan in a high altitude climber and suggest the addition of the term High Altitude Cough Syndrome (HACS) to the medical syntax to identify this discrete medical problem of exposure to very high altitude.