Real-time model uncertainty in the United States: the Fed from 1996-2003

We study 30 vintages of FRB/US, the principal macro model used by the Federal Reserve Board staff for forecasting and policy analysis. To do this, we exploit archives of the model code, coefficients, baseline databases and stochastic shock sets stored after each FOMC meeting from the model’s inception in July 1996 until November 2003. The period of study was one of important changes in the U.S. economy with a productivity boom, a stock market boom and bust, a recession, the Asia crisis, the Russian debt default, and an abrupt change in fiscal policy. We document the surprisingly large and consequential changes in model properties that occurred during this period and compute optimal Taylor-type rules for each vintage. We compare these optimal rules against plausible alternatives. Model uncertainty is shown to be a substantial problem; the efficacy of purportedly optimal policy rules should not be taken on faith. JEL Classification: E37, E5, C5, C6monetary policy, real-time analysis, uncertainty

Analysis of the gain distribution across the active region of InGaAs-InAlGaAs multiple quantum well lasers

Spectral gain measurements for two InGaAs-InAlGaAs multiple width quantum well structures, with inverse-configured active regions, have been presented. One structure consisted of wide quantum wells near the p-side and narrow quantum wells near the n-side of the active region. The other structure consisted of narrow quantum wells near the p-side of the active region with wider quantum wells near the n-side. It is shown that, for the same operating conditions, the structure with wide quantum wells on the p-side of the active region provided a 15% broader gain spectrum in comparison to the structure with narrow quantum wells on the p-side of the active region. The analysis of the results shows non-uniform carrier distribution across the active region of the structures, where the structure with wide quantum wells near the p-side of the active region provided 65% more gain in comparison to the structure with narrow quantum wells near the p-side of the active region. The gain distribution results have been compared with that obtained for the phosphorous quaternary structures in other literature and have shown there is some evidence to suggest that the gain distribution is more uniform in aluminium quaternary than phosphorous quaternary material

Primary cerebellopontine angle melanocytoma: review.

Introduction Primary cerebellopontine angle melanocytomas (PCPAMs) are very rare. Their natural history and prognosis are not fully understood. We reviewed the literature and add a new case to analyze PCPAM's presentation, radiological features, and outcome of treatment. Methods We performed a literature review using Medline, Embase, PubMed, and Cochrane databases. We searched for melanocytoma, melanoma, and pigmented tumors in the posterior cranial fossa and CPA to identify PCPAM. We have also searched our institution's neuro-oncology database. Results We identified 23 PCPAM from the literature and one case of our own. The mean age at presentation was 44.4 years with slight male preponderance. PCPAM presented with cerebellopontine angle (CPA) syndrome with or without hydrocephalus. Preoperative diagnosis was difficult; they appeared hyperintense on T1 and isointense on T2 magnetic resonance imaging (MRI) and enhanced with gadolinium. However, the final diagnosis was only made by immunohistochemical examination. Total surgical resection of PCPAM was associated with prolonged survival while subtotal excision was associated with frequent recurrence. Conclusion PCPAM are very rare and should be considered in the differential diagnosis of all CPA lesions that appear hyperintense on T1 and isointense on T2 MRI images. Patients with PCPAM should undergo total surgical resection to avoid fatal recurrences

Investigation of mid-infrared AlInSb LEDs with an n-i-p structure

We report on the investigation on mid-infrared AlInSb LEDs with an n-i-p structure. Compared to the conventional AlInSb LEDs with a p-i-n structure, a better current spreading corresponding to a uniform current distribution in the active region is expected in the n-i-p structure because of a high electron mobility in the n-type AlInSb material. The output optical power of laterally injected LEDs were investigated as a function of the device geometry by COMSOL simulations and confirmed by experimental results

Recent developments in optical fibre based optoelectronic oscillators

The paper reports recent progress on new types of low noise and high spectral purity optoelectronic oscillators operating at optical wavelengths around 1550nm and radio frequencies (RF) up to 40GHz with RF linewidths <1kHz