The Statistical Analysis of Experimental Data

A short-cut rule has been devised for dicotomous data and ill-conditioned quantitative data to test for a one-sided difference between two groups. The rule is defined in terms of a critical count (CC) and a critical difference (CD). For a CC of 4, 8, or 12 the .05 rule is CD equal to 4, 5, or 6, respectively, and the .Ol rule is CD equal to 5, 6, or 7, respectively.     

Logic programming to predict cell fate patterns and retrodict genotypes in organogenesis

Caenorhabditis elegans vulval development is a paradigm system for understanding cell differentiation in the process of organogenesis. Through temporal and spatial controls, the fate pattern of six cells is determined by the competition of the LET-23 and the Notch signalling pathways. Modelling cell fate determination in vulval development using state-based models, coupled with formal analysis techniques, has been established as a powerful approach in predicting the outcome of combinations of mutations. However, computing the outcomes of complex and highly concurrent models can become prohibitive. Here, we show how logic programs derived from state machines describing the differentiation of C. elegans vulval precursor cells can increase the speed of prediction by four orders of magnitude relative to previous approaches. Moreover, this increase in speed allows us to infer, or ‘retrodict’, compatible genomes from cell fate patterns. We exploit this technique to predict highly variable cell fate patterns resulting from dig-1 reduced-function mutations and let-23 mosaics. In addition to the new insights offered, we propose our technique as a platform for aiding the design and analysis of experimental data.     

On the Non-linear Damping of Mechanical Oscillators in Flows of 4He

In the studies of both classical and quantum turbulence, significant attention is devoted to the investigation of the behavior of various submerged resonators. Upon entering the turbulent regime, the oscillators start to experience a significant drag force, which varies non-linearly with velocity. We present an empirical way of modeling such systems, and calculate the expected resonant response of such oscillators near the fundamental frequency as a function of the applied driving force. We apply the model to the crossover from linear to non-linear drag forces and compare with previous models as well as selected experimental data on the transition to turbulence in oscillatory flow of ⁴He.     

Direct Determination of Energy Band Alignments of Ni/Al2O3/GaN MOS Structures Using Internal Photoemission Spectroscopy

The energy band alignments of Ni/Al₂O₃/GaN heterostructures have been explored by internal photoemission (IPE) and capacitance–voltage (CV) measurements. By performing IPE measurements at both reverse- and forward-bias conditions, the Ni/Al₂O₃ Schottky barrier is found to be 2.9 ± 0.1 eV with the presence of a strong image force lowering effect, while the Al₂O₃/GaN conduction-band offset is determined to be 2.2 ± 0.1 eV and is insensitive to oxide electrical field. CV-based flat-band voltage analysis has further been performed on samples with different oxide thicknesses, not only confirming the IPE-measured band alignment but also revealing the presence of 3.0 × 10¹² cm^-2 net positive charge at the Al₂O₃/GaN interface.     

The Acrylation of Glycerol: A Precursor to Functionalized Lipids

With the objective of expanding the number of functionalized lipids available, the reactive vinyl group of acrylic acid was introduced to triacylglycerol by esterification of glycerol. Didecanoylacryloylglycerol was synthesized from decanoic and acrylic acids and glycerol using K₂O as catalyst. 2 g (21.7 mmol) glycerol, 11.3 g (65.4 mmol) decanoic acid, 6.2 g (86.1 mmol) acrylic acid, 60 ml hexane, and 400 mg K₂O were added to 300-ml closed stainless steel reactor and maintained at 200 °C for 5 h. The resulting product, designated DDA, was isolated at about 40% yield based on the acylglycerol products. The other products included tridecanoylglycerol, diacryloyldecanoylglycerol, and the diacylglycerols of these acids. DDA was then converted to functionalized lipids by the Michael addition and Heck reaction. The Michael addition of thiophenol and 4-bromothiophenol yielded the corresponding linear thioethers whereas and Heck reaction products from bromobenzene and bromoanisole yielded triacylglycerols containing trans-cinnamic acid and trans-(4-methoxy)cinnamic acid, respectively.