Molecular structure and charge distribution in organometallics of the 4f and 5f elements V: crystal and molecular structure of tetrakis(ν-cyclopentadienyl)-thorium(IV) and the temperature dependence of its electrical dipole moment

The crystal and molecular structure of Th(C₅H₅)₄, was investigated by single crystal X-ray diffraction. The compound crystallizes tetragonal with a = 868.3(1), C = 1064.4(3) pm with two molecules per unit cell. The average Th—Cp distance of 260.6 pm is in good agreement with the predicted distance of 258.8 pm, and is larger than the corresponding distance of the uranium compound (253.8 pm). The temperature dependence of the dipole moment of the title compound, of thorium tetramethylcyclopentadienide (Cp′,Th), and of the homologous uranium compound in benzene solution is discussed with respect to their molecular structure.     

On-the-Fly Reseeding: A New Reseeding Technique for Test-Per-Clock BIST

In this paper we present a new reseeding technique for test-per-clock test pattern generation suitable for at-speed testing of circuits with random-pattern resistant faults. Our technique eliminates the need of a ROM for storing the seeds since the reseeding is performed on-the-fly by inverting the logic value of some of the bits of the next state of the Test Pattern Generator (TPG). The proposed reseeding technique is generic and can be applied to TPGs based on both Linear Feedback Shift Registers (LFSRs) and accumulators. An efficient algorithm for selecting reseeding points is also presented, which targets complete fault coverage and allows to well exploiting the trade-off between hardware overhead and test length. Using experimental results we show that the proposed method compares favorably to the other already known techniques with respect to test length and the hardware implementation cost.     

Trace elements bioaccumulation in Porcellionides pruinosus (Brandt, 1833) and related biomarkers of exposure

In the last years, the increase of anthropogenic activities has led to a progressive pollution of ecosystems. Oniscidean isopods are a group of terrestrial animals known as excellent bio‐indicators and bio‐accumulators, because of their capacity to accumulate contaminants and to implement appropriate strategies of detoxification. For this study, we collected Porcellionides pruinosus from two different sites in the Corinth region (Greece), a polluted site and a control site, to assess the heavy metal pollution status. We conducted an inductively coupled plasma mass spectrometry (ICP‐MS) analysis for the detection of trace elements in animals' hepatopancreas and soil; we performed also immunohistochemistry for detection of metallothioneins 1 (MT1) and heat shock protein 70 (HSP70s). The results suggest a great capacity of the species in trace elements bioaccumulation and the high degree of pollution of the area near Agioi Theodoroi where the metal pollution index (MPI) is threefolds higher than the control site, due to the presence of significantly higher concentration of arsenic, cadmium, cobalt, chromium, manganese, molybdenum, and lead found in hepatopancreas and soil. The environmental stress is confirmed by the expression of the relative biomarkers of exposure MT1 and HSP70. Our study, with a multimarker approach, consents getting a complete analysis of environmental quality and the effect of pollution on organisms and shows for the first time the heavy metals contamination status in certain Greece area. Furthermore, P. pruinosus proved to be an appropriate indicator of pollution in terrestrial ecosystems.     

Detection and mitigation of monitor identification attacks in collaborative intrusion detection systems

Collaborative defensive approaches such as collaborative intrusion detection system (CIDS) have emerged as a response to the continuous increase in the sophistication of cyberattacks. Such systems utilize a plethora of heterogeneous monitors to create a holistic picture of the monitored network. A number of research institutes deploy CIDSs that publish their alert data publicly over the Internet. This is important for researchers and security administrators, as such systems provide a source of real‐world alert data for experimentation. However, a class of identification attacks exists, namely probe‐response attacks (PRAs), which can significantly reduce the benefits of a CIDS. In particular, such attacks allow an adversary to detect the network location of the monitors of a CIDS. This article discusses the state of the art, with an emphasis on our previous and ongoing work, with regard to the detection and the mitigation of PRAs. We compare the most promising defensive mechanisms with respect to their effectiveness and the possible negative effects they might introduce to the CIDS. Finally, we provide a thorough discussion of research gaps and possible future directions for the field.     

Topological Based Scan Matching – Odometry Posterior Sampling in RBPF Under Kinematic Model Failures

Rao-Blackwellized Particle Filters (RBPF) have been utilized to provide a solution to the SLAM problem. One of the main factors that cause RBPF failure is the potential particle impoverishment. Another popular approach to the SLAM problem are Scan Matching methods, whose good results require environments with lots of information, however fail in the lack thereof. To face these issues, in the current work techniques are presented to combine Rao-Blackwellized particle filters with a scan matching algorithm (CRSM SLAM). The particle filter maintains the correct hypothesis in environments lacking features and CRSM is employed in feature-rich environments while simultaneously reduces the particle filter dispersion. Since CRSM’s good performance is based on its high iteration frequency, a multi-threaded combination is presented which allows CRSM to operate while RBPF updates its particles. Additionally, a novel method utilizing topological information is proposed, in order to reduce the number of particle filter resamplings. Finally, we present methods to address anomalous situations where scan matching can not be performed and the vehicle displays behaviors not modeled by the kinematic model, causing the whole method to collapse. Numerous experiments are conducted to support the aforementioned methods’ advantages.     

Spatially resolved electronic and vibronic properties of single diamondoid molecules

Diamondoids are a unique form of carbon nanostructure best described as hydrogen-terminated diamond molecules. Their diamond-cage structures and tetrahedral sp3 hybrid bonding create new possibilities for tuning electronic bandgaps, optical properties, thermal transport and mechanical strength at the nanoscale. The recently discovered higher diamondoids have thus generated much excitement in regards to their potential versatility as nanoscale devices. Despite this excitement, however, very little is known about the properties of isolated diamondoids on metal surfaces, a very relevant system for molecular electronics. For example, it is unclear how the microscopic characteristics of molecular orbitals and local electron-vibrational coupling affect electron conduction, emission and energy transfer in the diamondoids. Here, we report the first single-molecule study of tetramantane diamondoids on Au(111) using scanning tunnelling microscopy and spectroscopy. We find that the diamondoid electronic structure and electron-vibrational coupling exhibit unique and unexpected spatial correlations characterized by pronounced nodal structure across the molecular surfaces. Ab initio pseudopotential density functional calculations reveal that much of the observed electronic and vibronic properties of diamondoids are determined by surface hydrogen terminations, a feature having important implications for designing future diamondoid-based molecular devices.     

Calibration of tapping AFM cantilevers and uncertainty estimation: Comparison between different methods

We present a comparative study between three different methods for the spring constant calibration of silicon beam-shaped Atomic Force Microscope (AFM) cantilevers, used in tapping AFM mode in air. The geometries of these levers can be quite different from the standard rectangular cross section. We examine a method that combines the knowledge of cantilever dimensions and eigenfrequencies (Cleveland formula), the Sader method and we build cantilever models based on Finite Element Analysis (FEA). We demonstrate that with accurate measurement of dimensions, resonance frequency and quality factor, the Cleveland formula yields a combined cantilever stiffness uncertainty of approximately ±7% and the Sader method an uncertainty of ±5%. We also use FEA to show that when trying to approximate a realistic trapezoidal 3D tipped geometry, there exists a systematic overestimation in cantilever stiffness of ±2%, compared to when considering a simple rectangular cross section. Our constructed FE models are able to account for inhomogeneities in material properties as well as the influence of the added reflective coating in the cantilever stiffness estimation.