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Dominant mutations in the gene GJB2 cause keratitis-ichthyosis-deafness (KID) syndrome, a severe condition affecting the skin, cornea and inner ear. GJB2 encodes the protein connexin-26 (Cx26) which forms hemichannels or gap junction channels allowing the passage of signalling molecules. Approximately 80% of KID syndrome patients carry a c.148G > A (p.D50N) mutation in GJB2, which results in aberrant channel function. We hypothesised that silencing of the mutant allele in patient keratinocytes using allele-specific siRNA could correct the channel function. First, to confirm whether patient keratinocytes with only one wildtype GJB2 allele formed functional channels following allele-specific siRNA treatment, GJB2+/- keratinocytes were generated using CRISPR/Cas9. The scrape-loading dye transfer (SLDT) assay showed no distinguishable difference in gap junction intercellular communication (GJIC) between GJB2+/- and GJB2+/+ cells, suggesting normal GJIC in GJB2+/- keratinocytes. Nineteen siRNAs were designed and tested in HeLa cells expressing wildtype or mutant GJB2-GFP transgene. A lead siRNA, was discovered, which potently inhibited the mutant mRNA and protein without affecting wildtype GJB2 expression. The efficacy of the lead siRNA was assessed using keratinocytes derived from a KID syndrome patient (KID-KC) harbouring heterozygous c.148G>A mutation. These cells displayed pathological features of KID syndrome, with reduced gap junction plaque formation, impaired GJIC and hyperactive hemichannels confirmed by immunostaining, SLDT, patch clamp and neurobiotin uptake assays. Following treatment with the siRNA, selective silencing of mutant GJB2 allele in KID-KCs was confirmed at mRNA and protein levels. Significant improvement of GJIC and reversal of hemichannel activity were detected, with the latter corrected to a level comparable to that recorded in normal keratinocytes. Furthermore, RNA-Seq analysis showed that only six genes in the KID-KC transcriptome were significantly altered by the siRNA treatment, suggesting low-level off-target effects. In conclusion, allele-specific siRNA silencing of pathogenic dominant GJB2 mutation could be a potential therapeutic intervention for KID syndrome.

My dissertation consists of three essays. The first essay proposes a theory on the dynamics of productivity dispersion. In response to a negative profit shock, the leading firm responds by increasing R&D effort to recover the lost profit, while the laggard firm responds by reducing R&D effort because a lowered profit means a smaller return to innovation. Such heterogeneous R&D responses explain the observed countercyclical productivity dispersion. The second essay engages in an empirical study confirming the theory in the previous essay. Parametric and semi-parametric reduced-form regressions both exhibit heterogeneous responses in firms’ R&D intensity to the negative profit shock as suggested by my theory. A structural estimation of the model using GMM and data from U.S. manufacturing firms produces the heterogeneous R&D responses and the consequential larger productivity dispersion in response to a negative profit shock. The structurally estimated model also shows a higher productivity growth rate following the shock, which is due to the higher R&D effort exerted by the leading firm. The third essay focuses on the firm decision between R&D projects different in quality and time structure. With a theoretical model, I show that a temporary protectionist policy leads a positive measure of domestic firms to switch from the long-term to the short-term innovation project. It is because the policy raises the profitability of innovation in the short term, and some firms sacrifice quality for the timeliness of innovation as a response, resulting in a lower productivity growth rate. The above theory on firms’ decisions regarding R&D projects is motivated and verified by my empirical study of the 1986 U.S.-Japan semiconductor trade conflict.

MOF-5 has attracted considerable attention due to its ability to store gaseous fuels at low pressure with high densities. However, low thermal conductivity and limited robustness upon exposure to water and other reactive species are two challenges which limit the application of MOF-5. The focus of this dissertation is to understand and overcome these shortcomings through detailed experimental and computational characterization of the prototype compound, MOF-5. Improvements to the thermal conductivity of MOF-5 are demonstrated using densified pellets consisting of a physical mixture of MOF-5 and expanded natural graphite (ENG). We conclude that the low thermal conductivity typical of MOFs can be improved using a judicious combination of second phase additions and processing techniques. Regarding robustness, we first quantify experimentally the impact of humid air exposure on the properties of MOF-5 as a function of exposure time, humidity level, and morphology (i.e., powders vs. pellets). Densification into pellets can slow the degradation of MOF-5 significantly, and may present a pathway to enhance the stability of some MOFs. We subsequently examined the thermodynamics and kinetics of water adsorption/insertion into MOF-5 using van der Waals-augmented DFT calculations and transition state finding techniques. We find that incoming water molecules preferentially adsorb at adjacent sites on Zn-O clusters rather than filling widely separated low energy sites. Our calculations also suggest that the thermodynamics of MOF hydrolysis are coverage dependent, and that hydrolysis is slow at low water coverages and is preceded by an incubation period. The third component in our study of MOF-5 robustness involved cyclic and static exposure to impure hydrogen gas. MOF-5 was exposed to 5 gas mixtures over hundreds of adsorption/desorption pressure cycles and for extended periods of static exposure lasting up to 1 week. Hydrogen chloride was the only impurity that yielded a measurable decrease in hydrogen storage capacity. FTIR and XRD analyses reveal slight changes in the spectra only for those samples exposed to HCl and NH3 impurities. In closing, we briefly examine hydrogen permeation into- and the internal structure of- MOF-5 pellets using neutron and x-ray imaging techniques (tomography and radiography).

Under the assumption of a perfect gas with a constant specific heat ratio, the first approximation of the integral-relations method, which considers the entire shock layer as a single strip, is derived for axisymmetric bodies of arbitrary smooth contour. The resulting differential equations were then applied to a supersonic and hypersonic flow past a paraboloid of revolution. The shock shapes, shock wave detachment distances, locations of sonic lines; and velocity and pressure distributions for the body were calculated for γ = 1.4 and y = 5/3, and at Mach numbers of 3, 4, 6, 10 and 1000. These calculations were carried out on an IBM 1620 electronic computer. The results were compared with those obtained by Van Dyke's inverse method. The agreement between the two methods was found to be good, in view of the fact that only the first approximation of the integral relations method was used.