Test-Driven Development for Spreadsheet Risk Management

Spreadsheet technology is central to the functioning of the financial sector, but professionally created spreadsheets have a high level of error, which highlights the need for innovative supporting processes and tools. The current global financial crisis will likely accelerate this need because anticipated regulation will require novel, innovative risk management methods and technologies that cover development, risk assessment, review, and other spreadsheet activities. These methods will need to be easy to understand and use and will have to serve multiple stakeholders' needs. Test-driven spreadsheet development (TDSD) is one such method. TDSD provides an ideal fit with existing market-leading spreadsheet management processes and can assist managers and auditors in the assessment and control of spreadsheet risk.     

Physical origin of negative differential resistance in SOI transistors

From a two-dimensional solution of Laplace's equation it is shown that a significant increase in temperature occurs in the channel of SOI transistors due to the relatively poor thermal conductivity of the buried insulator. Based on this simulation an equation is derived which predicts that at small channel lengths the pinchoff point is shifted, an effect which is consistent with experimental observations. In addition, the positive 'kink' is reduced with the negative differential resistance, can be explained by a temperature increase in the channel.<>     

Synergistic interaction between paclitaxel and 8-chloro-adenosine 3',5'-monophosphate in human ovarian carcinoma cell lines

Taxol is a unique anticancer agent that is used in treatment of advanced ovarian cancer. Taxol exposure results in the polymerization and stabilization of the microtubule skeleton of eukaryotic cells, hence blocking replication and intracellular motility. 8-Chloro-adenosine 3',5'-monophosphate (8-Cl-cAMP) is a cAMP analogue, currently in Phase II clinical trials, that displays growth inhibition at micromolar concentrations. The aim of this study was to assess the nature of the interaction between 8-Cl-cAMP and paclitaxel using the combination index (CI) method of Chou and Talalay, which uses the median-effect analysis. Two ovarian cancer cell lines, A2780 and OAW42, which differ in sensitivity to both drugs, were tested using the fixed-ratio design using various scheduling regimens. Concurrent exposure of both drugs resulted in highly synergistic interactions in both cell lines. CIs (mean +/- SE) with this schedule were 0.182 +/- 0.016, 0.315 +/- 0.32, and 0.618 +/- 0.637 at 20, 50, and 80% cell kill, respectively, in A2780 cells and 0.001 +/- 0.0009, 0.016 +/- 0.0075, and 0.184 +/- 0.168 at 20, 50, and 80% cell kill, respectively, in OAW42 cells. In both cell lines, synergy was effective over a 4-fold log range of concentration for either drug. Sequencing with paclitaxel for 24 h prior to 8-Cl-cAMP was the most effective regimen; it resulted in consistently low CIs of up to the 90% cell kill level for both cell lines. Exposure to 8-Cl-cAMP prior to paclitaxel was the least effective regimen. In conclusion, the combination of paclitaxel and 8-Cl-cAMP is highly synergistic in ovarian carcinoma cell lines, suggesting that 8-Cl-cAMP may stimulate the antitumor effect of the taxanes.     

Structural Basis of Microtubule Stabilization by Discodermolide

Microtubule‐stabilizing agents (MSAs) are widely used in chemotherapy. Using X‐ray crystallography we elucidated the detailed binding modes of two potent MSAs, (+)‐discodermolide (DDM) and the DDM–paclitaxel hybrid KS‐1‐199‐32, in the taxane pocket of β‐tubulin. The two compounds bind in a very similar hairpin conformation, as previously observed in solution. However, they stabilize the M‐loop of β‐tubulin differently: KS‐1‐199‐32 induces an M‐loop helical conformation that is not observed for DDM. In the context of the microtubule structure, both MSAs connect the β‐tubulin helices H6 and H7 and loop S9–S10 with the M‐loop. This is similar to the structural effects elicited by epothilone A, but distinct from paclitaxel. Together, our data reveal differential binding mechanisms of DDM and KS‐1‐199‐32 on tubulin.     

A simple technique for measuring the generation lifetime inSOI-substrate material using the principle of charge centroids

A charge-time measurement, utilizing the charge-centroid principle, is presented for the rapid assessment of silicon-on-insulator (SOI) substrates. The technique is applicable to technologies which involve the formation of a buried dielectric layer with a thin-film body region wherein devices are formed. The measurement is routine and only requires a simple two-terminal SOI capacitor from which the quality of the body region, as indicated by the lifetime, can be assessed prior to device fabrication. This measurement can be carried out on any combination of dopant type. All parameters required by the analysis are obtainable from a simple two-terminal CV plot     

Position control of an Ionic Polymer Metal Composite actuated rotary joint using Iterative Feedback Tuning

Ionic Polymer Metal Composites (IPMCs) are a novel material that has been the subject of considerable interest over recent decades because of their unique electrochemical and mechanical properties which allow them to be used as smart transducers. However, there has been insufficient research to determine if the electro-active polymer can reliably actuate common engineering mechanisms due to its nonlinear and time-variant nature. This paper explores a model-free approach for controlling the position of an IPMC actuated rotary linkage for micro-manipulation. The mechanism was developed based on the mechanical characteristics of the IPMC actuators. A Proportional, Integral (PI) controller was initially developed and tested to control the tip displacement of the mechanism. Test results show that this classical controller is capable of actuating the rotary mechanism to microscopic deflections but would not completely stabilise at the steady state position. An adaptive, nonlinear tuning method called Iterative Feedback Tuning (IFT) was developed to tune the performance of the PI controller. Empirical results show that the new control scheme improved the steady state response. However, the enhancement of the transient response could not be definitively validated as solely the work of the IFT algorithm due to the time-variant and variable response behaviour of IPMCs.     

Experimental determination of magnitude of selfheating and its influence on breakdown in silicon-on-insulator transistors

When silicon-on-insulator transistors are operated at high power levels significant selfheating is known to occur. The associated increase in the operating temperature can result in a change in the breakdown voltage through the temperature dependence of the multiplication process. Here, the maximum temperature rise, which occurs in the drain depletion region, is measured by monitoring the thermally generated leakage current. The dependence of the multiplication process on temperature is also measured. The work demonstrates that device selfheating together with the temperature dependence of the multiplication process must be accounted for if drain current/drain voltage breakdown is to be accurately predicted.<>     

Fixed latency on-chip interconnect for hardware spiking neural network architectures

Information in a Spiking Neural Network (SNN) is encoded as the relative timing between spikes. Distortion in spike timings can impact the accuracy of SNN operation by modifying the precise firing time of neurons within the SNN. Maintaining the integrity of spike timings is crucial for reliable operation of SNN applications. A packet switched Network on Chip (NoC) infrastructure offers scalable connectivity for spike communication in hardware SNN architectures. However, shared resources in NoC architectures can result in unwanted variation in spike packet transfer latency. This packet latency jitter distorts the timing information conveyed on the synaptic connections in the SNN, resulting in unreliable application behaviour.