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1. The sensitometric characteristics of photographic plates exposed to hydrogen peroxide and developed are strikingly similar, both for time of exposures, time of development, and intensity i.e., concentration). Characteristic curves similar to H. and D. curves were obtained, including a period of “reversal.”2. A tentative theory of the action of hydrogen peroxide is suggested. It is supposed that the decomposition of peroxide is chemi-luminiscent, short wave-length radiation being afforded at the surface of the silver halide grain, and particularly at check the hypothesis that these nuclei consist of colloid silver.The authors desire to express their thanks to Mr. R. F. Quirk and Mr. E. Huberth for painstaking assistance in the experi- mental work, and to Miss Anber J. Benedict for making the pH measurements. 相似文献
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It is very difficult, if not impossible, to remove the last traces of hypo from photographic papers by any known procedure of washing. The sulfur in the residual hypo ultimately, and especially under abnormal conditions of temperature and humidity, combines with the silver image to form yellowish brown silver sulfide. This phenomenon is known as sulfiding or “fading” of the image. The various factors which affect the rate of fading of images and the washing out of hypo from films and papers are outlined.Chemical methods of hypo elimination have been proposed from time to time but the majority of these have not been satisfactory because they tend to leave substances such as thionates in the photographic material, which are equally as difficult to wash out as hypo and which also tend to sulfide or fade the silver image. A new hypo eliminator is recommended consisting of two volatile chemicals, hydrogen peroxide and ammonia. This eliminator oxidizes the hypo to sodium sulfate, which is inert and soluble in water, while any excess eliminator evaporates on drying.Two formulas and treatments are proposed: (1) Complete elimination of hypo for use by the professional, advanced amateur, and photofinisher who demand the highest standard of photographic quality in their prints.(2) Almost complete elimination of hypo (less than o.oi milligram per square inch).Since the conditions to which prints will be subjected are rarely known in advance, use of the “complete elimination treatment” is advised in all cases. 相似文献
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K.T. Bainbridge 《Journal of The Franklin Institute》1931,212(4):489-506
A short review is included of previous work on the blackening of photographic plates by positive rays and rays of an analogous nature.The blackening of Eastman x-ray plates, by positive ions, has been measured as a function of the energy of the ions of Li, Na, K, Rb, and Cs. The energy of the ions required to produce a photographic density of D = 0.3 with a one minute exposure at a current density of 1.32 × 10?8 amperes per cm.2 ranged from 1420 electron-volts in the case of cæsium to 860 electron-volts in the case of Li7. Approximately 105 ions are required at these energies to render developable one silver-halide grain. For a threshold density, D = 0.04, under the same conditions the energy ranged from approximately 920 to 460 electron-volts for Cs and Li7 respectively.Sensitivity comparisons were made between x-ray plates and process and schumannized process plates. Potassium ions with an energy as low as 137 electron-volts were recorded on Schumann plates, and it is possible that positive ions of one-third this energy can be recorded. 相似文献
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A silver nitrate test is described for the quantitative determination of residual hypo in photographic prints. The hypo is converted in situ to silver sulfide, the transmission density of the sulfide determined, and the hypo content obtained by reference to a standard curve.The method used to establish the standard curve is outlined, the data being verified by quantitative analyses.A simplified procedure is suggested involving the application of a drop of silver nitrate to the back of the print and then matching the spot visually with a set of standards. 相似文献
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(1) A method of preparing photohalide emulsions somewhat different from that of Lüppo-Cramer has been worked out, using either colloidal silver or colloidal silver sulphide as the sensitizer.(2) Treatment of the plates containing this emulsion with chromic acid to remove excess colloidal silver also lowers sensitivity considerably. This sensitivity can be restored by an after-treatment of the plates with a very dilute ammonia solution.(3) The photohalide emulsion prepared as described showed, with one exception, a broader spectral sensitivity than those prepared without colloidal silver or silver sulphide. This agrees with the previous work of others on photohalide emulsions.(4) The spectral sensitivity of such emulsions differs from those sensitized with allyl-thiourea sensitizer in being more sensitive in the red and less sensitive in the green region of the spectrum.(5) The present work supports the strain-ionic deformation hypothesis of sensitivity proposed by Sheppard, Trivelli and Loveland. It does not, however, exclude the hypothesis of Hickman as to the role played by the silver sulphide sensitizing speck. 相似文献
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芥川龙之介因为受中国古典文学的影响．所以认为中国是一个神秘、美好的国家．中国人都是充满英雄色彩的豪杰．但是在他的中国之行后．这种认识发生了变化——对当时的中国现状及中国人感到了失望．这种对中国认识的变化影响了芥川的文学创作。本文试在前人研究的基础上探寻芥川对中国认识的变化过程并分析对其文学创作的影响。 相似文献
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P H Smith 《Isis; an international review devoted to the history of science and its cultural influences》1999,90(3):420-461
This article argues that the art collection owned by Franciscus dele Bo?, Sylvius, a professor of practical medicine at the University of Leiden from 1658 to 1672, gives insight into some aspects of the character and significance of the new philosophy in the midseventeenth century. Through his teaching, his advocacy, and his practice of the new experimental philosophy, Sylvius played a role in shaping and institutionalizing the practices of the new philosophy that spread throughout Europe in the late seventeenth and eighteenth centuries. Sylvius's house design and large painting collection also exemplified the consumption and taste of the northern Netherlands in the seventeenth century. An examination of both Sylvius's science and his taste can help us understand what was at stake for Sylvius and his contemporaries in their practice of the new philosophy. This article finds that Sylvius's taste and his science both involved practices of social distinction, demarcation, and control. Moreover, both were enmeshed in controversy about the epistemological status of knowledge gained through the senses and about the practices by which that knowledge was gathered. 相似文献
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Ramalingam C 《Endeavour》2008,32(3):86-93
As an image-making tool for scientists studying the transient, instantaneous photography has long been seen as opening up a visual realm previously inaccessible to the inferior testimony of the human eye. But when photographic pioneer Henry Fox Talbot took the first photograph of a moving object by the light of an electric spark in 1851, he was guided by existing visual practices designed to create instantaneous vision in the eye itself. Exploring the background behind the peculiar subject of his experiment - a mechanically spinning disc - reveals a hidden prehistory of spark-illuminated photography: physicists' pre-photographic techniques for stopping time. 相似文献
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A century before the outbreak of bovine spongiform encephalopathy (BSE), Great Britain and North America grappled with pleuro-pneumonia - a disease in cattle that had equally maddening consequences. Towards the end of the 19th century, this condition was at the heart of a transatlantic trade dispute that lasted for decades and attracted the attention of livestock farmers, diplomats, shipping moguls, veterinarians, public health regulators and journalists the world over. Scientific controversy aggravated the situation when there were doubts about the scientific judgment of Privy Council veterinary officials, who were simultaneously conducting disease-diagnosis activities and pushing for tighter regulations at British ports. At this point, William Williams, principal of the New Veterinary College in Edinburgh, waded into this troubled arena. His strong convictions spawned a long-running disagreement with the British Government over the diagnoses of pleuro-pneumonia in cattle imported from the USA and Canada. 相似文献
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Rudge DW 《Public understanding of science (Bristol, England)》2005,14(3):249-268
H.B.D. Kettlewell is famous for several investigations conducted in the early 1950s on the phenomenon of industrial melanism, which are widely regarded as the classic demonstration of natural selection. In a recent (2002) book-length popularization of this episode in the history of the science, science writer Judith Hooper draws attention to what she interprets as discrepancies in the results reported by Kettlewell in his first scientific papers on the subject. On the basis of correspondence among Kettlewell and his associates, a survey of scientific publications that mention outstanding questions surrounding the phenomenon, as well as interviews with his son, surviving colleagues, and scientists who have worked on industrial melanims, Hooper all but explicitly concludes that Kettlewell committed fraud. The following essay critically examines her evidence in support of this allegation, including her discussion of his character, the alleged motives, and whether fraud was even committed. None of Hooper's arguments is found to withstand careful scrutiny. The concluding section draws several conclusions about how history of science should be depicted to the public. 相似文献
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Heat transfer in laminar tube flow with convective boundary conditions and axial heat conduction in the fluid is solved exactly. The effects of the external Biot numbers and the axial conduction in fluid on the temperature distribution and the local Nusselt number are determined for both the upstream and the downstream regions. In order to illustrate the effects of velocity profile, the results for the slug flow and the parabolic velocity profiles are plotted simultaneously. The heat transfer characteristics of the flow are found to be rather sensitive to the Péclét number, the external Biot numbers and the velocity profile in the thermal entrance region. 相似文献
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Making sense of global warming: Norwegians appropriating knowledge of anthropogenic climate change 总被引：1，自引：0，他引：1
Ryghaug M Sørensen KH Naess R 《Public understanding of science (Bristol, England)》2011,20(6):778-795
This paper studies how people reason about and make sense of human-made global warming, based on ten focus group interviews with Norwegian citizens. It shows that the domestication of climate science knowledge was shaped through five sense-making devices: news media coverage of changes in nature, particularly the weather, the coverage of presumed experts' disagreement about global warming, critical attitudes towards media, observations of political inaction, and considerations with respect to everyday life. These sense-making devices allowed for ambiguous outcomes, and the paper argues four main outcomes with respect to the domestication processes: the acceptors, the tempered acceptors, the uncertain and the sceptics. 相似文献
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通过黄万里的18封信,马力和张玉美回忆了他们的老师。黄万里不仅向他们传授了专业知识,而且也成为他们心目中真正的热爱祖国和人民的楷模。他的言论和行为均出自对国家和人民的忠诚和责任感,而非出自一己之私利。 相似文献
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Sigmund K. Waldorf 《Journal of The Franklin Institute》1932,213(6):605-622
If the amplifier-oscillograph is to attain the fidelity of frequency reproduction of the unaided oscillograph, the amplifier circuit must be designed, constructed, and used with discretion. In no portion of the circuits, in neither the amplifier itself nor the connected measuring circuits, is it permissible for the associated resistances, capacitances, and inductances to produce time constants so large as to suppress any of the frequencies which the oscillograph vibrator would reproduce normally. Steadiness of the amplifier is a prime consideration, usually attainable with moderately high gain units by having sure electrical contacts and the component parts operated conservatively within their respective ratings. Interference is frequently a source of considerable difficulty and great care must be exercised not to permit it to cause erroneous measurements.A method of compensating for the steady component of the amplifier output current has been investigated and when properly used, has been found neither to impair the sensitivity of the instrument appreciably nor to require critical adjustment.Consideration also has been given to the photographic technique involved in oscillography in order that its full possibilities might be realized.An instrument has been described and discussed which had a sensitivity of about 1.7 millivolts per mm. deflection. When the maximum permissible input resistance of 0.1 megohm was used, a current sensitivity of about 1.7 × 10?8 amperes per mm. deflection was attained. A greater value of input resistance could not be used without the possibility of introducing serious distortion. 相似文献