Ofthe Mean Research Articles

The faint limit of the Hubble Space Telescope faint object spectrograph and rejection of the cosmic-ray background

The faintest object which can be observed with the Hubble Space Telescope (HST) Faint Object Spectrograph (FOS) is set by the detector cosmic-ray background and not by object flux. We use data from Beaver and Lyons to show that 48% of the background counts are from cosmic rays which each generate a near instantaneous burst of two or more counts. Setting the FOS threshold parameter REJLIM = 1, which rejects all frames with more than one count increases the ratio of signal-to-dark counts (S/D) by a factor of 1.94, regardless of the frame time or the object signal, because half of the dark counts which arrive in single counts (from either cosmic-ray bursts or thermal dark current photoemission) are rejected at the same rate as the object signal. But the signal-to-noise ratio (SNR proportional to S/square root of S + D) increases by at most a factor of 1.35, and for realistic parameters and taking into account dead time, we expect a gain in SNR of only 1.18. If a diode has failed and now emits noise, no data at all will be recorded. The chance of this occurring is approximately = 10% , and for this reason we do not recommend the use of REJLIM. The two-point correlation function of dark counts per pixel has strong peaks every four pixels, caused by the action of quarter-stepping on the counts from large bursts. The counts from such bursts spread over at least 80-100 diodes, and we show that such bursts can be rejected during data reduction if the data are recorded in RAPID mode with individual exposures of about 35 seconds. The SNR of the spectrum can also be improved by weighting each exposure by its SNR (a function ofthe mean dark count rate at that time), since dark varies by a factor of 2 around an orbit. These two procedures together increase the SNR by a factor of 1.1.3 (a 28% gain in exposure time) in regions of a spectrum where the object is much fainter than the background. We find that the Ly-alpha and O I sky emission lines give at most 4 (counts/array/s/sq arcsec), and typically half this number. With a small frame time and a small entrance aperture, these counts cause REJLIM = 1 to reject only a few percent of the data. We discuss only the HST FOS blue side detector, but the same ideas apply to any photon counter which records bursts of noise, and the calculations resemble those for the loss of signal due to coincidences in photon counters. In the ideal photon counter the dark counts are readily distinguished from photons. One way to do this is to add detectors which records only dark current, so that every cosmic ray produces more than one count and the instrument can be operated in an anti-coincidence mode.

The nonperturbative wave functions, transverse momentumdistribution and QCD vacuum structure

It is shown that there is one-to-one correspondence between two, apparently different problems: (1) The determination ofthe mean values of transverse moments 〈 k ⊥ 2n 〉 for the nonperturbative pion wave function ψ ( k ⊥ 2, x) and (2)The evaluationof the mixed vacuum condensates 〈 q ̄ G μν nq〉 . Arguments in favor of a large magnitude of the mixed vacuum condensate 〈 q ̄ (igσ μνG μν) 2q〉 are given. The analysis isbased on the dispersion relations and PCAC. Because of the large values of the condensates we found a noticeable fluctuationof the momentum 〈 k ⊥ 4〉 > 〈 k ⊥ 2〉 2 . We also found some general properties of the condensates 〈 q ̄ (igσ μνG μν) nq〉 for arbitrary n. This information is used for the analysis of the higher moments 〈 k ⊥ 2n〉 in the limit when the space-time dimension d → ∞. As a byproduct, it is proven that the standard assumption on factorizability of the ψ( k ⊥ 2, x) = ψ( k ⊥ 2) ψ (x) does contradict the very general properties of the theory. We define and model ψ( k ⊥ 2, x) , satisfying all these constraints.

The Strategies of Politeness in the Chinese Language (review)

296 China Review International: Vol. ?, No. ?, Spring 1994 Studies in China; they are problems that still exist today. Inclusion ofa briefdiscussion of such issues, with views from both the American and Chinese sides, would have been a valuable addition to the directory. Frank Tang University ofHawai'i Kaidi Zhan. The Strategies ofPoliteness in the ChineseLanguage Berkeley: Institute ofEast Asian Studies, University of California, Berkeley, Center for Chinese Studies, 1992. xv, 106 pp. This is a compact book about a very complicated subject: the linguistic means and strategies for achieving politeness in Mandarin Chinese. Authored by a native Chinese speaker, the bulk ofit consists of conversational snippets and utterances and capsule explanations cataloged under the typology of universal politeness strategies developed earlier by anthropologically trained linguists Penelope Brown and Stephen Levinson. In constructing their typology, Brown and Levinson had treated face—and the avoidance of face threats to self and others— as the underlying imperative for much of routine polite communication; in addition , they regarded politeness as the underlying imperative for many deviations from maximally efficient communication. The author's Chinese examples are largely culled from contemporary Chinese literature, the Chinese classic Dream ofthe Red Chamber, and recorded conversations; they are presented in both simplified characters and pinyin, followed by their English translation. Throughout, the author tries to compare and contrast differences in politeness choices and conventions between Chinese and English speakers, and to explain their potential for cross-cultural confusion. Linguist Robin Lakoffprovides a lengthy preface to help acquaint the reader with the book's pragmatic focus, its intended audience (linguists, sociologists, psychologists, anthropologists, language learners, and teachers), and to underscore the pertinence ofpoliteness to comparative understandings of sociability and culture. In her introductory chapter, the author presents some distinctive grammatical possibilities available to Chinese politeness strategies. Chinese, for example, has special suffixes, particles, and reduplicated verbs that can be used either to soften or to vivify or to convey cooperation or commiseration. The author also attributes Chinese politeness strategies to unique cultural and psychological incopyright \994fluences. Theyinclude a traditional sense ofsocial hierarchy, strong kin sentiby University ofments, the Confucian Doctrine ofthe Mean and the Confucian stress on modHawai 'i Presseration, and other values such as modesty, prudence, kindness, compassion, Reviews 297 solicitousness, optimism, showing respect to one's elders and betters, and putting others first. She enlists these language-specific and culture-specific features in her next three chapters to illustrate Chinese versions of the three superpoliteness strategies charted by Brown and Levinson: (1) positive, that is, "familiar," politeness— redressive speech that seeks to develop greater warmth and closeness between interlocutors by showing special regard for the addressee's virtues, abilities, possessions , achievements, or condition; (2) negative, that is, "respectful," politeness— redressive speech that is distancing and seeks to preserve an addressee's need for privacy, autonomy, or freedom from imposition; and (3) off-record politeness— redressive speech delivered roundaboutly or ambiguously in a way that, in effect, lets a speaker offthe hook or, at least, doesn't put anyone on the spot. The first two superpoliteness strategies are complementary on-record strategies that, writes the author, are more elaborate and more frequently used than are offrecord politeness strategies among Chinese. In their positive politeness strategies, for example, Chinese might address others (i.e., neighbors, friends, and even strangers and serious lovers) as kinfolk; they might also signal their commonality in dialect or locality, or give explicit recognition to their shared status as old schoolmates or former work mates, or they might lexically acknowledge a master-apprentice, teacher-student relationship . At other times, Chinese might shift to the addressee's reference point by substituting the verb complement -qu"go" for -Zai"come" or by switching from speaker focus to speaker-addressee focus through specialized pronominal use, that is, zanmen "inclusive we" or ni (jiu) shuo "you (just) say." They avoid disagreements by offering vague responses, token agreements, or white lies. Unlike English, which uses conventional, generalized forms, Chinese greetings are concretely directed to an addressee's health ("Have you recovered yet?") or to whether the addressee has taken a meal yet ("Have you had your breakfast/lunch/ dinner?"), and their partings are full ofgentle admonishments about safety ("Be careful...

L'acte du vote en situation de crise. L'Amérique centrale

Vote In critlcal situations. The case of central America. Olivier Dabène. [84-92]. This article analyses a certain number of characteristics of tbe way people vote in a crilical situation. Among otber tbings, an attempt is made to assess the conditions in whicb such a situation arises. As a basis of this analysis, tbe author bas first studied bow people learn bow to vote, specially the way it happened in central America under autboritarian regimes. It has had a durable impact on tbe behaviors of the voters : voters forming herds or even groups of supporters, festivities marking the occasion, results being regarded witb scepticism or even derision. He bas then described the conditions prevailing in a critical situation (lack of mobility of voters, presence of the militaty,...). Finally, he gives an account ofthe meaning of that voting in a time of crisis bas for tbe voters : a return to democracy in the case of elections taking place after dictatorship and a transition towards establishing peace and achieving economie reconstruction. Tbe author doubts that the appearance of the implemenls used in elections contributes to the consolidation of demoracy.

Variability of Electrofishing Crew Efficiency, and Sampling Requirements for Estimating Reliable Catch Rates

Abstract Comparisons of electrofishing catch rates were conducted on two lakes in central Florida; sampling precision was examined in five other lakes. Significant differences were found among crews for various sizes (adults, subadults, quality) of largemouth bass Micropterus salmoides, bluegill Lepoinis inacrochirus, and redear sunfish L. microlophus. Results were not consistent between lakes, and rankings of crew catches varied among size categories. The number of samples required to estimate largemouth bass catch per minute with confidence limits that are within 10% of the mean at the 80% confidence level ranged from 4 to 110 (median, 19), based on catch rates from seven central Florida lakes. From 2 to 28 samples (median, 5) would be required to estimate largemouth bass catch per unit effort within 20% of the mean. For bluegill, the number of samples required to yield confidence limits within 20% of the mean ranged from 4 to 83 (median, 17). Precision ofwithin 20% ofthe mean is recommended for fisheri...

68 NUTRITIONAL STATUS OF PATIENTS IN A PEDIATRIC HOSPITAL II BIOCHEMICAL ASPECTS

A nutrition survey including biochemical and immunologic indicators was performed to establish the prevalence of malnutrition in hospitalized pediatric patients. Serum albumin levels & hematocrit were determined by micromethod expressing results as %ofthe mean normal level for age.Cellular inmunity was evaluated by skin tests to PPD and Candida Albicans. One hundred and sixty patients (age range 2 months to 16 years)were studied. Low serum albumin was found in 14% of all patients,in 7% of the medical and 28% of the surgical group.A negative relationship was found between lenght of stay and albumin levels. Normal albumin was found in 95% of patients with low W/H.Low hematocrit for age was found in 28% of all patients with a higher prevalence in medical patients(39% vs 18%).Infants studied had rates of low Hto comparable to the normal population, older children differed showing higher rates. A scarr as evidence of BCG was found in 82% of all cases,34% of which were PPD +.Skin test for candida were + in 32% of all patients. One or more positive skin tests were found in 42%, both test were negative in 48%.An important age related decrease in % positive for both tests was observed. No association was found relating albumin, W/H and skin tests. But a significant relationship was observed relating Arm Muscle Area to skin tests. These results suggest that patients present predominantly marasmus and some mild Kwashiokor protein energy malnutrition. A high rate of altered cell mediated inmunity was found amongst the patients studied.