Can a "credit crunch" be efficient?

Two observations have sometimes been viewed as evidence that the equilibrium allocations of intermediated credit markets are inefficient. First, low-income households' marginal propensity to consume is close to unity. Second, even high-income households seem to face nonprice constraints during recessions. This paper presents a model that possesses both of these features. (A recession is modeled as an economy in which the equilibrium level of investment is at its lowest possible level.) However, contrary to the conventional view, the equilibrium of this model is ex ante efficient. The model also sheds light on some historical episodes of credit restraint.Credit

Activation of Egr-1 expression in astrocytes by HIV-1 Tat: new insights into astrocyte-mediated Tat neurotoxicity

Human immunodeficiency virus type 1 (HIV-1) Tat plays an important role in HIV-associated neuropathogenesis; the underlying mechanisms are still evolving. We have recently shown that HIV-1 Tat induces expression of glial fibrillary acidic protein (GFAP), a characteristic of HIV-1 infection of the central nervous system (CNS). We have also shown that the Tat-induced GFAP expression in astrocytes is regulated by p300, and that deletion of the early growth response 1 (Egr-1) cis-transacting element within the p300 promoter abolishes Tat-induced GFAP expression. In this study, we further examined the relationship between Tat and Egr-1 in astrocytes. We found increased Egr-1 protein expression in Tat-expressing human astrocytoma cells and mouse primary astrocytes. Using the Egr-1 promoter-driven firefly luciferase reporter gene assay and the site-directed mutagenesis, we demonstrated that Tat increased Egr-1 expression by transactivating the Egr-1 promoter and involving specific serum response elements (SRE) within the promoter. Consistent with these data, we showed that Tat transactivation of the Egr-1 promoter was abrogated when astrocytes were cultured in serum-reduced media. Taken together, these results reveal that Tat directly transactivates Egr-1 expression and suggest that Tat interaction with Egr-1 is probably one of the very upstream molecular events that initiate Tat-induced astrocyte dysfunction and subsequent Tat neurotoxicity

Three point functions of N=4 Super Yang Mills from light cone string field theory in pp-wave

In this paper we calculate three-string interaction from light cone string field theory in pp-wave. We find exact agreements with the free planar three point functions of non-chiral BMN operators of ${\cal N} = 4$ super Yang Mills. The three string interaction vertex involving the Neumann matrices was derived in a recent paper hep-th/0204146. We explicitly calculate the bosonic Neumann matrices in the limit of large $\mu p^{+} \alpha^{'}$ . Using the Neumann matrices we are able to compute the cubic interactions of three string modes in a pp-wave background.Comment: 9 pages, no figure. V2: typos corrected, some changes in introduction, a mistake in Section 2 and Appendix corrected. V3: more typos corrected and minor change

String Pair Creations in D-brane Systems

We investigate the criterion, on the Born-Infeld background fields, for the open string pair creation to occur in D$p$-(anti-)D$p$-brane systems. Although the pair creation occurs generically in both D$p$-D$p$ and D$p$-anti-D$p$ systems for the cases which meet the criterion, it is more drastic in D$p$-anti-D$p$-brane systems by some exponential factor depending on the background fields. Various configurations exhibiting pair creations are obtained via duality transformations. These include the spacelike scissors and two D-strings (slanted at different angles) passing through each other. We raise the scissors paradox and suggest a resolution based on the triple junction in IIB setup.Comment: V2. 1+28 pages, 5 figures in JHEP3, minor changes, added reference

Feedback from the IR Background in the Early Universe

It is commonly believed that the earliest stages of star-formation in the Universe were self-regulated by global radiation backgrounds - either by the ultraviolet Lyman-Werner (LW) photons emitted by the first stars (directly photodissociating H_2), or by the X-rays produced by accretion onto the black hole (BH) remnants of these stars (heating the gas but catalyzing H_2 formation). Recent studies have suggested that a significant fraction of the first stars may have had low masses (a few M_sun). Such stars do not leave BH remnants and they have softer spectra, with copious infrared (IR) radiation at photon energies around 1eV. Similar to LW and X-ray photons, these photons have a mean-free path comparable to the Hubble distance, building up an early IR background. Here we show that if soft-spectrum stars, with masses of a few M_sun, contributed more than 1% of the UV background (or their mass fraction exceeded 90%), then their IR radiation dominated radiative feedback in the early Universe. The feedback is different from the UV feedback from high-mass stars, and occurs through the photo-detachment of H^- ions, necessary for efficient H_2 formation. Nevertheless, we find that the baryon fraction which must be incorporated into low-mass stars in order to suppress H_2-cooling is only a factor of few higher than for high-mass stars.Comment: Accepted for publication in MNRAS (Letters). 5 pages with 2 figure

CQAR: Closed quarter aerial robot design for reconnaissance, surveillance and target acquisition tasks in urban areas

International Journal of Computational Intelligence, Volume 1, Number 4, 2004. Retrieved April 2006 from http://prism2.mem.drexel.edu/~paul/papers/ohIjci2004.pdfThis paper describes a prototype aircraft that can fly slowly, safely and transmit wireless video for tasks like reconnaissance, surveillance and target acquisition. The aircraft is designed to fly in closed quarters like forests, buildings, caves and tunnels which are often spacious but GPS reception is poor. Envisioned is that a small, safe and slow flying vehicle can assist in performing dull, dangerous and dirty tasks like disaster mitigation, search-and-rescue and structural damage assessment

Cost-effectiveness of a medication event monitoring system for tuberculosis management in Morocco

BACKGROUND: Digital health technologies have been used to enhance adherence to TB medication, but the cost-effectiveness remains unclear. METHODS: We used the real data from the study conducted from April 2014 to December 2020 in Morocco using a smart pillbox with a web-based medication monitoring system, called Medication Event Monitoring Systems (MEMS). Cost-effectiveness was evaluated using a decision analysis model including Markov model for Multi-drug resistant (MDR) TB from the health system perspective. The primary outcome was the incremental cost-effectiveness ratio (ICER) per disability adjusted life-year (DALY) averted. Two-way sensitive analysis was done for the treatment success rate between MEMS and standard of care. RESULTS: The average total per-patient health system costs for treating a new TB patient under MEMS versus standard of care were $398.70 and$155.70, respectively. The MEMS strategy would reduce the number of drug-susceptible TB cases by 0.17 and MDR-TB cases by 0.01 per patient over five years. The ICER of MEMS was $434/DALY averted relative to standard of care, and was most susceptible to the TB treatment success rate of both strategies followed by the managing cost of MEMS. CONCLUSION: MEMS is considered cost-effective for managing infectious active TB in Morocco

Autonomous hovering of a fixed-wing micro air vehicle

Paper presented at the 2006 IEEE International Conference on Robotics and Automation, ICRA 2006, Orlando, FL.Recently, there is a need to acquire intelligence in hostile or dangerous environments such as caves, forests, or urban areas. Rather than risking human life, backpackable, bird-sized aircraft, equipped with a wireless camera, can be rapidly deployed to gather reconnaissance in such environments. However, they first must be designed to fly in tight, cluttered terrain. This paper discusses an additional flight modality for a fixedwing aircraft, enabling it to supplement existing endurance superiority with hovering capabilities. An inertial measurement sensor and an onboard processing and control unit, used to achieve autonomous hovering, are also described. This is, to the best of our knowledge, the first documented success of hovering a fixed-wing Micro Air Vehicle autonomously

A MAV that flies like an airplane and hovers like a helicopter

IEEE/ASME International Conference on Advanced Intelligent Mechatronics (AIM), Monterey, CA, pp. 699-704, July 2005Near-Earth environments, such as forests, caves, tunnels, and urban structures make reconnaissance, surveillance and search-and-rescue missions difficult and dangerous to accomplish. Micro-Air-Vehicles (MAVs), equipped with wireless cameras, can assist in such missions by providing real-time situational awareness. This paper describes an additional flight modality enabling fixed-wing MAVs to supplement existing endurance superiority with hovering capabilities. This secondary flight mode can also be used to avoid imminent collisions by quickly transitioning from cruise to hover flight. A sensor suite which will allow for autonomous hovering by regulating the aircraft’s yaw, pitch and roll angles is also described

Geometric Transition versus Cascading Solution

We study Vafa's geometric transition and Klebanov - Strassler solution from various points of view in M-theory. In terms of brane configurations, we show the detailed equivalences between the two models. In some limits, both models have an alternative realization as fourfolds in M-theory with appropriate G-fluxes turned on. We discuss some aspects of the fourfolds including how to see the transition and a possible extension to the non-supersymmetric case.Comment: 34 pages, LaTex, 2 figures; v2: Some comments added and references updated. Final version to appear in JHE