Endogenous Credit Cycles

We build a model in which verifiability of private debts, timing mismatch in debt settlements and borrowing leverage lead to liquidity crisis in the financial market. Central bank can respond to the liquidity crisis by adopting an unconventional monetary policy that resembles repurchase agreements between the central bank and the lenders. This policy is effective if the timing mismatch is nominal (i.e., a settlement participation risk). It is ineffective if the timing mismatch is driven by a real shock (i.e., preference shock).liquidity problem, timing mismatch, leveraging, liquidity shock, settlement risk, repurchase agreement, consumption shock

A boundary integral equation approach to three dimensional electromagnetic wave scattering problems

Electromagnetic scattering models are finding increasing interest in many applications ranging from nondestructive evaluation (NDE) to design of optical systems. The availability of a computational scattering model characterizing the underlying system serves several purposes. First, it serves as an inexpensive test bed to simulate a variety of test situations. For instance, the forward model can be used to evaluate various polarizations and incidence angles of the incident source fields and the corresponding spatial distribution of the scattered fields which in turn provides information useful for optimizing the measurement of scattered fields. By preserving some of the realism that is usually possible in purely analytical methods, it provides valuable insight into the physics of actual problems. Second, forward scattering models are important in solving the inverse problem where the scattered fields are used for characterizing the size, the shape and the constitution of the scatterer;The development of theoretical models largely relies on the use of numerical techniques such as boundary element method (BEM), finite element method (FEM), or finite difference method (FDM). However, no single numerical method has emerged as the optimal method for solving all electromagnetic scattering problems. One numerical method might be preferred over others, depending on the nature of the problem. For instance, problems which involve homogeneous scatterers and propagation of waves in an infinite medium are typically solved using the BEM whereas problems which involve a naturally truncated region are modeled using FEM and FDM;This dissertation presents a boundary integral equation (BIE) formulation for the problem of electromagnetic scattering due to homogeneous dielectric scatterers. The governing BIEs are then evaluated numerically using the BEM. Several fundamental electromagnetic scattering geometries are considered. The first problem involves solving for the scattered fields in the presence of a single, three dimensional, arbitrarily shaped, dielectric scatterer suspended in an infinite medium. The formulation is then extended to modeling the scattered fields in the presence of multiple dielectric scatterers as well as a dielectric scatterer in the proximity of an infinite perfect conducting plane. Lastly, the problem of a dielectric scatterer situated close to a dielectric half-space is discussed. The geometries are chosen so that the work presented in this dissertation will serve as a basic model and solutions to a large range of problems can be obtained by modifying one or more of the configurations presented

Transcriptional activation by the Myb proteins requires a specific local promoter structure

AbstractThe biological effects of the cellular c-Myb and the viral v-Myb proteins are strikingly different. While c-Myb is indispensable for normal hematopoiesis, v-Myb induces acute leukemia. The v-Myb DNA-binding domain (DBD) differs from that of c-Myb mainly by deletion of the first of three repeats which correlates with efficient oncogenic transformation and a decrease in DNA-binding activity. To investigate the difference in DNA-binding and transcriptional activation, oligonucleotide selection and electrophoretic mobility shift assays were employed. The v-Myb DBD (R2R3) shows an intrinsic DNA-binding specificity for an AT-rich downstream extension of the Myb recognition element (MRE) PyAACT/GG for efficient binding to this site, whereas R1 within the c-Myb DBD allows for more flexibility for this downstream extension. Therefore, due to the presence of repeat R1, c-Myb can bind to a greater number of target sites. The intrinsic DNA-binding specificity of R2R3 is further supported with the results from in vivo transcriptional activation experiments which demonstrated that both the v-Myb and c-Myb DBDs require an extension of the MRE (motif #1) by a downstream T-stretch (motif #2) for full activity. Surprisingly, the T-stretch improves binding when present on either strand, but is required on a specific strand for transcriptional activation

A Kinase Chaperones Hepatitis B Virus Capsid Assembly and Captures Capsid Dynamics in vitro

The C-terminal domain (CTD) of Hepatitis B virus (HBV) core protein is involved in regulating multiple stages of the HBV lifecycle. CTD phosphorylation correlates with pregenomic-RNA encapsidation during capsid assembly, reverse transcription, and viral transport, although the mechanisms remain unknown. In vitro, purified HBV core protein (Cp183) binds any RNA and assembles aggressively, independent of phosphorylation, to form empty and RNA-filled capsids. We hypothesize that there must be a chaperone that binds the CTD to prevent self-assembly and nonspecific RNA packaging. Here, we show that HBV capsid assembly is stalled by the Serine Arginine protein kinase (SRPK) binding to the CTD, and reactivated by subsequent phosphorylation. Using the SRPK to probe capsids, solution and structural studies showed that SRPK bound to capsid, though the CTD is sequestered on the capsid interior. This result indicates transient CTD externalization and suggests that capsid dynamics could be crucial for directing HBV intracellular trafficking. Our studies illustrate the stochastic nature of virus capsids and demonstrate the appropriation of a host protein by a virus for a non-canonical function

Configurationally stable, enantioenriched organometallic nucleophiles in stereospecific Pd-catalyzed cross-coupling reactions: an alternative approach to asymmetric synthesis

Several research groups have recently developed methods to employ configurationally stable, enantioenriched organometallic nucleophiles in stereospecific Pd-catalyzed cross-coupling reactions. By establishing the absolute configuration of a chiral alkyltin or alkylboron nucleophile prior to its use in cross-coupling reactions, new stereogenic centers may be rapidly and reliably generated with preservation of the known initial stereochemistry. While this area of research is still in its infancy, such stereospecific cross-coupling reactions may emerge as simple, general methods to access diverse, optically active products from common enantioenriched organometallic building blocks. This minireview highlights recent progress towards the development of general, stereospecific Pd-catalyzed crosscoupling reactions using configurationally stable organometallic nucleophiles