Direct Diode Pumped Raman Amplifier Based on a Multimode Graded Index Fiberr

The direct pumping of a Raman fiber amplifier (RFA) was attempted using an array of four 25W, fiber pigtailed diodes at 936nm, combined via a 7 channel fiber beam combiner. The initial attempt was conducted using a 1.8 km, 100 micron core, GRIN fiber with an NA of .29 and attenuation 3.6 dB/km at 936nm. While amplification was not achieved, over 200mW of conversion was shown, with 10.4W of pump power and 3.5W of seed. This corresponds to an average conversion efficiency of 2.2%. The subsequent effort utilized a 2km long, 200 micron core, GRIN fiber, with NA of .27 and attenuation of 2.8dB/km at pump wavelength. Again, amplification was not achieved, but a gain of 80mW was present, with 3.5W of seed power and 14W of pump. This corresponds to an average conversion efficiency of 0.6% and only 2.5% of the coupled seed power. The final experiment attempted to solve the problem of coupling efficiency and high Raman threshold by utilizing a 50/250 dual-clad fiber, with NAs of .28 and .46 for the core and inner cladding, respectively. Again, amplification was not realized, as only 100mW of gain was present, with 25W of pump and 4.2W of coupled seed power, corresponding to 36% of the coupled seed, and an average conversion efficiency of only 0.4%. Although amplification was not achieved for any of the three fibers, gain was shown possible in all, showing that directly pumping an RFA with a diode source is possible

Leveraging the fullest potential of scientific collections through digitisation.

Access to digitised specimen data is a vital means to distribute information and in turn create knowledge. Pooling the accessibility of specimen and observation data under common standards and harnessing the power of distributed datasets places more and more information and the disposal of a globally dispersed work force, which would otherwise carry on its work in relative isolation, and with limited profile and impact. Citing a number of higher profile national and international projects, it is argued that a globally coordinated approach to the digitisation of a critical mass of scientific specimens and specimen-related data is highly desirable and required, to maximize the value of these collections to civil society and to support the advancement of our scientific knowledge globally

Pre-Hospital Management of Acute Myocardial Infarction

Atherosclerosis of the coronary arteries is recognized today as a major health problem in the United States, since 600,000 deaths are attributed to it annually (Vital Statistics 1966). The medical profession and the general public are well aware of the important studies of its pathogenesis and prevention. However, the profession has been so preoccupied with these phases of investigation that the mechanism of death and possible modes of correction have remained obscured until recently

Patterns of Interstate Migration in the Mid-2000s: Are Racial Groups Moving in Different Directions?

Patterns of U.S. Interstate Migration in the Mid-2000s: Are Racial Groups Moving in Different Directions? Abstract This research examines interstate in-movement, out-movement, and resulting patterns of net internal migration of Blacks, Asians, Hispanics, and non-Hispanic Whites in the United States, using data from the 2005-2007 American Community Survey. One goal is to learn how similar or dissimilar members of these four broad racial categories are in entering and exiting different U.S. states, and thereby to contribute to ongoing research on differential spatial relocation of racial groups (e.g., are these groups moving to different sets of states?). A second goal is to learn how Black, Asian, Hispanic, and White net internal migration levels correlate with economic, demographic, and social characteristics of the states. Results show that similarities in patterns of Black, Asian, Hispanic, and White in-, out-, and net migration overshadow differences. For each race the states with high (or low) numbers and rates of in- and out-movement are largely the same. White and Hispanic interstate mobility patterns show the greatest similarity, Black and Asian the least. Moreover, these racial categories resemble each other in how their net internal migration correlates with economic and social characteristics of U.S. states. Results also suggest regional variation: in the South, states with economic and social characteristics indicative of higher “development” have higher net internal migration for all races, but in the North those states with higher development characteristics have lower (often negative) net internal migration

Introduction

This issue of the Medical College of Virginia Quarterly is devoted to the publication of the proceedings of the Cardiac Arrhythmias Symposium held at the Cavalier Hotel in Virginia Beach, Virginia from June 8-10, 1972. The reason for such emphasis upon the field of cardiac arrhythmias is primarily due to the fact that there has been an awakened interest in recent years in the problem of sudden death. It is now being appreciated that a significant number of deaths attributed to cardiovascular disease are due to cardiac arrhythmias, a potentially correctable disorder

Introduction

This issue of the Medical College of Virginia Quarterly is an edited form of the proceedings of the Cardiac Pacing symposium held in Williamsburg, Virginia on April 16 and 17, 1971. The program emphasized the clinical aspects of cardiac pacing, and the format was structured with formal presentations followed by panel discussions

Polluters’ Profits and Political Response: Direct Control versus Taxes: Comment

In a recent issue of this Review, James Buchanan and Gordon Tullock (B-T) presented a public choice analysis of the relative merits of direct controls and taxes in externality control. In Section IV of their paper, B-T consider the case of reciprocal external diseconomies of consumption. They ask whether ... persons in this sort of interaction, acting through the political processes of the community, will impose on themselves either a penalty tax or direct regulation (p. 143). Their analysis is carried out within the context of a two-person model in which each person consumes the same quantity of a good (or carries out the same quantity of an activity) in the precontrol equilibrium, but in which the two transactors exhibit different price elasticities of demand for the good. B-T show that under these circumstances the imposition of equal quotas would be preferred to the imposition of an efficient tax by one transactor but not the other. Their analysis that supports that conclusion is incorrect

An index approach to measuring product differentiation : a hedonic analysis of airfares

The main objective of this paper is to introduce an Allen-type index of differentiation based on cost functions. With this index, we create an economic measure of product differentiation that quantifies differences between products. Applied research has some generally accepted economic measures, for example, the Herfindahl-Hirschman Index for market concentration, or the Gini coefficient for inequality. Product differentiation, however, does not yet have an established measure. Our objective is to fill that gap and introduce a measure that can be used in market-related applied research such as market power, antitrust, price indexes, or market strategy. To operationalize the index, we introduce the concept of a core product and use cost functions to measure the degree of differentiation from the core product. To demonstrate the use of the index, we study the effect of product differentiation on price formation in the airline industry using an enhanced hedonic model. The model is empirically tested on 103,980 observations of quarterly US domestic airfare data between 2002 and 2016 and shows that product differentiation has a significant effect on both price and mark-u

The Habeas Corpus Revolution: A New Role for State Courts.

This Article’s purpose is to portray recent changes in the United States Supreme Court’s habeas corpus jurisprudence—limiting the scope of the federal writ while reducing the federal judiciary’s role overseeing the criminal justice systems. Seemingly, the Court gave little thought to whether this reduction in federal oversight should be accompanied by a greater measure of review on the part of state courts. The writ of habeas corpus, often referred to as the Great Writ, is the primary means of enforcing rights guaranteed under the United States Constitution and federal courts are the principal guardians of these rights. While commitment to this principle remains constant, application of the remedy of federal habeas corpus to state convictions is inconsistent. Case law points to the Court’s rejection of the argument that limiting federal habeas review will cause state judges to enforce federal constitutional rights less vigorously. State-court decisions may ultimately provide empirical data that will prove or disprove this hypothesis. Because recent restrictions on availability of the writ are due to judicial discretion rather than an absence of judicial authority, the Supreme Court remains free to remedy any perceived abuses or inequities in the current habeas regime. Congress, too, certainly could amend the habeas statutes to broaden the scope of federal review. Thus, the present era of limited federal oversight of state criminal processes may not endure. For now, it is important for states to seize their new responsibilities; they should abandon the old working hypothesis which generally denied state relief because multiple opportunities for federal relief lay ahead. An ideal criminal justice system should detect and correct serious errors early in the process, thus saving both the defendant and society the burden of repetitious litigation