Three-terminal devices to examine single molecule conductance switching

We report electronic transport measurements of single-molecule transistor devices incorporating bipyridyl-dinitro oligophenylene-ethynylene dithiol (BPDN-DT), a molecule known to exhibit conductance switching in other measurement configurations. We observe hysteretic conductance switching in 8% of devices with measurable currents, and find that dependence of the switching properties on gate voltage is rare when compared to other single-molecule transistor devices. This suggests that polaron formation is unlikely to be responsible for switching in these devices. We discuss this and alternative switching mechanisms.Comment: 5 pages, 4 figures. Supporting material available upon reques

Controlling charge injection in organic field-effect transistors using self-assembled monolayers

We have studied charge injection across the metal/organic semiconductor interface in bottom-contact poly(3-hexylthiophene) (P3HT) field-effect transistors, with Au source and drain electrodes modified by self-assembled monolayers (SAMs) prior to active polymer deposition. By using the SAM to engineer the effective Au work function, we markedly affect the charge injection process. We systematically examine the contact resistivity and intrinsic channel mobility, and show that chemically increasing the injecting electrode work function significantly improves hole injection relative to untreated Au electrodes.Comment: 5 pages, 2 figures. Supplementary information available upon reques

New Records of Michigan Cicadidae (Homoptera), With Notes on the Use of Songs to Monitor Range Changes

We present records of Diceroprocta vitripennis, Tibicen chloromera, and Tibicen pruinosa (new state record) in Michigan. Monitoring geographic range changes and population size differences by song suggests several population situations for cicadas: (1) sizable populations in most areas of apparently good habitat; (2) widely separated single individuals or small populations on the edges of populated regions, representing range extensions that may be of limited duration; (3) one or a few individuals present only once, probably transferred in soil on roots, and ultimately unsuccessful. Species- specific calling songs allow sensitive measurement of species\u27 range changes

Anatomy of sartorius muscle

A sartorius muscle is the longest muscle of the human system. It runs over 2 joints— hip and knee joints. In the study 10 sartorius muscles were examined. They were dissected free of lower human limbs. Dimensions of limbs which these muscles come from and dimensions of the muscles and their component parts were examined. The attention was paid mainly to parts of tendon located inside the muscle belly. The results show that they are either of a comparable length (distal tendon) or several times longer (proximal tendon) than visible parts located outside of the muscle. Moreover, a complex structure of the distal tendon which includes 2 tracts of different places of insertion was stated. Inferior tract inserted in the same place as muscle tendons: semitendinosus and gracilis. The superior tract inserted transversely against the former one. The tendon of the sartorius muscle forms additionally an aponeurosis whose fibres enter into the deep fascia of crus. The muscle belly is characterised with various width on different levels of its length. In half of casess word-like distal segment of belly is formed

Anatomy of the long peroneal muscle of the leg

Background: The aim of the work was to perform a morphometric analysis of the long peroneal muscle (LPM) of the leg and explore the relationship between muscle belly and tendon. Materials and methods: Ten lower limbs (8 right and 2 left) were fixed in formaldehyde and dissected using standard technique. The LPM was exposed from the proximal attachment to the top of a lateral malleolus. Results: The tendon was subsequently freed and various measurements were taken. The tendon of the LPM enters deep into the muscle belly. Muscle fibres surround the tendon and descend as far down as 4 cm above the lateral malleolus. Muscle fibres insert mainly along posterior border of the tendon and on its medial surface, leaving lateral surface only partly covered. Conclusions: The LPM contains a long intramuscular segment of the tendon and area of the musculotendinous junction varies along the LPM. It makes the idea of uniform pennation pattern of the LPM unlikely

Morphology and morphometry of the semitendinosus distal tendon in adults and foetuses

Background: The distal tendon of the semitendinosus is often used as a graft in orthopedic reconstructive surgery. Knowledge of the exact morphology of this tendon, and also the ability to predict its morphometric data are certainly helpful when planning the procedure of surgery. Comparison of the semitendinosus distal tendon anatomy in adults and foetuses may be scientifically relevant. There are no scientific reports on this tendon anatomy in foetuses. Materials and methods: Seventy semitendinosus muscles from cadavers were obtained using standard dissection techniques (50 muscles were obtained from adults and 20 from foetuses). Moreover, ultrasound examinations of 20 muscles were performed in living individuals. Results: Two main parts of the distal tendon were distinguished — the external part not covered with muscle fibres and the internal part, which is partially or entirely hidden within the muscle belly (venter). The average length of the distal tendon was 32.34 cm, while the average lengths of the external and internal parts were 9.65 cm and 12.59 cm, respectively. The external part was solid and cylindrical. The internal part was flat and rolled like a trough, thus making the tendon a poor transplant material. Similarly, the distal tendon in foetuses consisted of two parts, including the external and internal part. Conclusions: The proportions between the lengths of different muscle parts were very similar in adults and foetuses

Diversity of coronary arterial tree in laboratory mice

Background: Research on the development and topography of mouse coronary arteries has been conducted for many years. Patterns of the course of these vessels have been described in various mouse strains. Our research focused on hearts of MIZZ mice. Materials and methods: We visualised the coronary artery system by means of latex dye perfusion via the aorta. The injected latex did not reach the capillary vessel system. Results: The heart of MIZZ mice is supplied with blood by two main coronary arteries: the right and the left one. They deliver blood to the right and left part of the heart, respectively. The right coronary artery arises from the right sinus of the aorta and the left coronary artery from the left sinus. The interventricular septum is usually supplied by the septal artery, which is the main branch of the right coronary artery. All arteries of the coronary system run intramurally. The number of branches and the location of their ostia differed among the examined individuals. Conclusions: Detailed information about the normal topography of coronary arteries, the number and course of their branches, as well as the area of the heart which is vascularised by these vessels constitutes the basic knowledge necessary to conduct further experiments

Influence of the carbon substitution on the critical current density and AC losses in MgB2 single crystals

The DC magnetization and AC complex magnetic susceptibilities were measured for MgB2 single crystals, unsubstituted and carbon substituted with the composition of Mg(B_0.94C_0.06)2. The measurements were performed in AC and DC magnetic fields oriented parallel to the c-axis of the crystals. From the DC magnetization loops and the AC susceptibility measurements, critical current densities (Jc) were derived as a function of temperature and the DC and AC magnetic fields. Results show that the substitution with carbon decreases Jc at low magnetic fields, opposite to the well known effect of an increase of Jc at higher fields. AC magnetic losses were derived from the AC susceptibility data as a function of amplitude and the DC bias magnetic field. The AC losses were determined for temperatures of 0.6 and 0.7 of the transition temperature Tc, so close to the boiling points of LH2 and LNe, potential cooling media for magnesium diboride based composites. The results are analyzed and discussed in the context of the critical state model.Comment: 10 pages, 7 figures, 1 tabl

Kondo resonances and anomalous gate dependence of electronic conduction in single-molecule transistors

We report Kondo resonances in the conduction of single-molecule transistors based on transition metal coordination complexes. We find Kondo temperatures in excess of 50 K, comparable to those in purely metallic systems. The observed gate dependence of the Kondo temperature is inconsistent with observations in semiconductor quantum dots and a simple single-dot-level model. We discuss possible explanations of this effect, in light of electronic structure calculations.Comment: 5 pages, four figures. Supplementary material at http://www.ruf.rice.edu/~natelson/publications.htm

Universal Scaling of Nonequilibrium Transport in the Kondo Regime of Single Molecule Devices

Scaling laws and universality are often associated with systems exhibiting emergent phenomena possessing a characteristic energy scale. We report nonequilibrium transport measurements on two different types of single-molecule transistor (SMT) devices in the Kondo regime. The conductance at low bias and temperature adheres to a scaling function characterized by two parameters. This result, analogous to that reported recently in semiconductor dots with Kondo temperatures two orders of magnitude lower, demonstrates the universality of this scaling form. We compare the extracted values of the scaling coefficients to previous experimental and theoretical results.Comment: 4.5 pages, 3 figure