Alex Córdoba-Aguilar, Daniel M. González-Tokman, in 北京城市文化竞争力全国居首, 2014
5 Male Terminal Investment
Animals use different reproductive strategies across their lifetimes, strongly depending on their prospects for future reproduction (McNamara & Houston, 1996; Williams, 1966). A combination of age and physiological state (healthiness) will define to a great extent which strategy an individual will use (McNamara & Houston, 1996; McNamara, Houston, Barta, Scheuerlein, & Fromhage, 2009). In some cases, when animals are old or ill, they can wait for more favorable conditions and save their acquired resources for future chances of reproduction in more favorable conditions. On the other hand, old or ill animals probably will not have chances to reproduce in the future, and they could allocate all their energy to current reproduction, even if it results in physiological deterioration (McNamara et al., 2009). This last strategy is known as terminal investment. Given their high investment in reproductive events, rubyspot damselfly males are excellent models to study terminal investment: a male pays a high cost to obtain territories and matings, so that reproductive decisions are not trivial for their reproductive success. Terminal investment in males has been experimentally explored in H. americana by manipulating life expectancy of young and old males with nylon implants, which activate the insect's immune response (González-Tokman, González-Santoyo, & Córdoba-Aguilar, 2013). Compared to young males, that reduce the intensity of their sexual behavior when immune challenged, presumably as a cautious strategy, old males continue intense territorial defense, presumably as a terminal investment strategy (González-Tokman, González-Santoyo, & Córdoba-Aguilar, 2013). Such changes in sexual activity are reflected in fat reserves, which are strongly depleted in old males that are immune challenged (González-Tokman, González-Santoyo, & Córdoba-Aguilar, 2013). Despite the behavioral and physiological changes that result from terminal investment, they surprisingly have no effect on male survival, neither under natural nor under captive conditions (González-Tokman, González-Santoyo, Munguía-Steyer, et al., 2013). This suggests that the effects of terminal investment during senescence are somehow counteracted, probably with adaptive (presumably feeding) behavior, which would allow individuals to compensate for the resources used by the immune system (González-Tokman et al., 2011) leading to high survival. Changes in feeding behavior in response to terminal investment and senescence still need to be addressed.
Snacks foods are not equally viewed by everyone, and how a specific food is described can influence an individual’s perception. A recent qualitative study reported that snack foods were not always perceived as “real food” by mothers . In fact, when serving snacks, mothers more often attempt to manage their children’s behavior rather than consider snacking as a way to provide nutritious foods. Different cognitive representations about what is a meal versus a snack may also influence intake. Capaldi et al. showed that when isocaloric preloads were given to participants, but presented either as a snack or as a meal, a lower intake was observed following the preload described as a meal than when described as a snack . With regards to healthy eating, findings, from the literature that we recently reported in a review, suggest that various cognitive factors, such as type of food and branding, can significantly influence perceived healthiness of food via judgmental bias. However, impacts on food choice and intake are not always observed . A study showed that perceiving a snack food (i.e., oatmeal-raisin cookies) as healthy significantly increased undergraduate female students’ intake of that food by 35% (i.e., 56 kcal) during an ad libitum single meal in comparison to a condition in which the same food was perceived as unhealthy . The “healthy” snack was also seen as not only healthier but also more appropriate to eat. No differences between measured and self-reported snack intakes were observed which suggest that participants generally regarded it as normal to have a high intake of healthy foods. On the other hand, in a larger study conducted among men and women, verbal nutrition claims significantly influenced perceived healthiness of the snack food, but no impact was observed on food intake . Wansink and Chandon have also addressed this issue, and reported an increased caloric intake of 28% among participants when chocolate candies were labeled as low in fat than when labeled as regular . Overweight participants also appeared to be more inclined to eat in the low-fat labeling condition compared to the normal-weight participants, as their intake increased by 47% (vs 16% for normal-weight participants). A recent systematic review reported that attentional bias toward food cues varied between individuals, with an enhanced reactivity to food cues observed among overweight and obese individuals compared to normal-weight ones . We are currently surrounded by numerous nutrition claims and logos that appear on food labels and advertising as well as by information published by the media or on various websites. All of these cognitive influences, often identified by the concept of “health halos,” could positively influence energy balance while snacking. In fact, various food marketing strategies, such as branding, food claims, or food pricing, can bias food consumption and lead us to eat more than expected , and possibly without being aware of these overeating habits.
Even very young infants prefer attractive faces, a preference that is more marked for female than male faces. The preference is for a face constructed from average features, an appearance that would be unusual in real life. The preference for average features may either reflect an evolutionary preference for healthiness or a cognitive schema that enables facial recognition. These are not studies examining infants’ preferences for body shapes or types, though these could certainly be done using the preferential looking paradigm used in facial attractiveness research.
6.The Stock Market Plunge The report shows that compared with that in 2015, the percentage of graduates to start up business are significantly decreased from 6.3% to 3.1% in 2016. Local residents living near the launch sites have complained that the activists are putting their lives at risk by making them potential targets for North Korean retaliation. 该项目在毕业3年后的职业晋升方面排名第二。Tiemba项目的毕业生数量迄今只有约250人，使他们成为一个精英团体。 ? The failure of a backup generator forced the evacuation of the Langone Medical Center, part of NYU hospital. About 200 patients had to be moved. Officials are investigating why the backup power failed. ● “特朗普为想要离开美国的公民提供非洲或墨西哥单程机票”
When Dickens wrote about the French Revolution in A Tale of Two Cities, he did it with nearly a century of hindsight. Here, at the end of December, I don’t enjoy that luxury. As such, some of the trends I’ve written here are likely to remain in force for the foreseeable future, while others may have already begun to fade. As one of this period’s “noisiest authorities,” I insist only on your receiving this review with just one caveat in mind: Past performance does not guarantee future results. 结果发现，被要求画出单词的参与者能够更准确地记起这些单词。而且画本身的质量并不会对记忆效果有什么影响，帮助记忆的仅仅是“画画”这个动作。对于香蕉，画一个大概的轮廓和详细的画出每个细节，产生的作用是一样的。参与者们即使只是花上几秒来画画，也能在记忆结果上有显著提高。研究人员还计划进一步地引进更复杂的单词甚至观点表述来观察参与者记忆表述的准确度。 The last leg of the year is set to be a busy one for initial public offerings on both sides of the Atlantic, with companies including Italy’s Pirelli, Alibaba-backed Best Logistics and video streaming platform Roku lining up to list. I can't stop thinking that these children are my age, that it makes a tremendous difference where you are born, that I could be one of those children living in the Favellas of Rio; I could be a child starving in Somalia; a victim of war in the Middle East or a beggar in India. 我永远不能忘记这些和我同龄的孩子，当你出生的时候，他和我们真的很不相同，我也许生活在贫民窟，也可能是终日饿着肚子的小孩，也可能是中东战争的牺牲品，或者印度的小乞丐。 social Enrollment: 511 罗宾哈丁(Robin Harding) 帕拉莫尔《欢笑过后》 金维刚表示：“2016年居民消费价格指数仅同比上涨2%，低于预期的预测指标。属于温和通胀范围，反映了物价水平得到有效控制并保持基本平稳。” 据《21世纪经济报道》称，广东去年的GDP增速为7.5%。 Jia Yongsheng general director of the demolition company told China's state TV channel CCTV: 'For this kind of large-scale blasting demolition conducted in the downtown area we not only need to guarantee the demolition result but also strictly control the adverse effects of blasting.' 有关她在片中角色的细节尚未披露。 我们不希望通过贬值来增加出口，这不利于企业转型升级。 普斯·格洛（Pussy Galore）在本书中回归，这也是首次有邦女郎在邦德身边昙花一现后，拥有了自己的故事线。 adj. 笨拙的，尴尬的，（设计）别扭的 天生脑瘫的余秀华原本过着平静的乡村生活。现在，她在文坛引起了轰动，她描写情欲的生动诗歌“有明显的血污”。 In China, there were still 43 million people in rural areas living in poverty at the end of 2016. The country aims to help all of them out of poverty by 2020. 5. What Is Illuminati? 根据独立健康慈善金基金的分析，到2021年，医疗预算将持续缩减大概8亿欧元（超过10亿美金），尤其是在性健康和性传染病方面的缩减。
卡尔森一向热衷于歌唱事业和歌剧事业，因而这样的工作对她再合适不过了。 No Bad Manners Awards could be complete without a mention of a Kardashian, could it? That brought the balance of trade to $49.06bn, down about $4.3bn from November and coming in about $2.3bn lower than forecast. Over the past 20 years, at least 133,000 units in the city have gone market rate because of this rule, according to the Rent Guidelines Board. If the trend continues, rent stabilization could be further weakened, undermining Mayor de Blasio’s efforts to preserve affordable housing, say supporters of the policy. 由于合并后的航空公司通常继续分别公布航班延误统计数据，我们可能需要几年时间，才能看到全新美国航空公司在假日旅行方面表现如何。 2005年，戴维森发现自己总是得跟在一岁大的儿子杰克后面，收拾他随处乱扔的儿童吸管杯。于是，她从塔吉特（Target）上买了一台缝纫机，为儿童吸管杯设计出一个类似皮带的奇妙装置——SippiGrip。但她并没有很快实现自己的创业梦想——她加入了微软人力资源团队，与X-Box部门合作。2007年，她在全国性贸易展上推出了SippiGrip。幸运的是，塔吉特邀请她参加2008年父母发明产品计划。目前，戴维森的产品已经在沃尔玛（Walmart）、婴儿反斗城（Babies "R" Us）和亚马逊等零售商开卖。 6. “The Martian” With its red-rock buttes and mesas, Ridley Scott’s deeply satisfying space western both draws from an enduring genre and his own Pantheon legacy. (Read the review.) 社交名媛卡戴珊8月份参加凯莉·詹娜的19岁生日聚会时，笨手笨脚从跑车出来的方式让她不小心走光太多了。 Song “Family”(Tan Jing) Rana Foroohar The Chinese-made 3D fantasy/adventure film "Monster Hunt" broke a string of box-office records on its release in the country in July 2015, becoming the highest grossing film of the year in the Chinese mainland.
The second explanation for mortality crossovers is that they are produced by poor data quality. It is hypothesized that age misreporting in death statistics and/or censuses biases mortality estimates downwards at the oldest ages. Age overstatement has been considered the most common form of age misreporting, although other patterns have also been recorded (Ewbank 1981, Preston et al. 1999). Coale and Kisker (1986) concluded that the mortality crossovers they observed between developed and developing country populations were caused by poor data quality. Age misreporting has also been implicated in the black/white mortality crossover in the United States and the low mortality among Hispanics at older ages. Other potential explanations for the low mortality of Hispanics include the positive selection of migrants on such characteristics as healthiness and the difficulty of following the foreign-born in US death records (Elo and Preston 1997).
Preston et al. (1999) have shown that various patterns of age misreporting—net age overstatement, net age understatement, and symmetric age misreporting—bias mortality estimates downwards at the oldest ages. The downward bias is produced by all methods of mortality estimation the authors considered: conventional methods derived from vital statistics and censuses; longitudinal studies where age is identified at baseline; variable-r procedures based on age distribution of the population; variable-r procedures based on age distribution of deaths; and extinct generation methods. Thus, it is not unreasonable to propose that age misreporting at the oldest ages has led to downwardly biased death rates at the oldest ages and spurious mortality crossovers.
The most extensive studies of the potential impact of age misreporting on mortality crossovers pertain to the racial crossover in the Unites States. There is a general agreement that age misreporting has seriously biased African American death rates downwards at the oldest ages. The first study to document inconsistencies in age reporting for African Americans and whites in vital statistics and census data was the 1960 Matched Records study, which linked death certificates registered in May to August in 1960 to the 1960 Census of Population. For less than half of the nonwhite male and female matched cases was the age in the two sources identical. Age reporting was far better for whites. After the data were corrected for age misreporting, the racial crossover in mortality moved from the age interval 75 to 79 to the last open-ended age interval, 85 and older (Kitagawa and Hauser 1973).
Two recent matched-record studies of death certificates from the 1980s for whites and African Americans to early census records for these same individuals when they were children or adolescents continue to show substantial age misreporting for African Americans in death statistics at the oldest ages, but minimal problems for whites. Thus, conventionally constructed death rates from vital statistics and census data for African Americans continue to be seriously understated at the oldest ages. In contrast, death rates for whites do not show a systematic bias. A comparison of mortality rates for blacks and whites based on corrected data continue to reveal a mortality crossover for males in the age interval 95+ and for females at ages 90–94 (Preston et al. 1996, Hill et al. 2000). Age-specific death rates for this comparison are, however, based on somewhat unconventional variable-r procedures and on a very small number of deaths for African Americans at the oldest ages. They do not provide conclusive evidence of whether the racial crossover in mortality is real.
坦白地说，这部电影2017年可能筹备不好，但是以防万一我们还是把它归进来。这是拉斯洛.奈迈施的第二部电影，2016年早些时候他凭借《索尔的儿子》摘得奥斯卡最佳外语片。《日落》是一部关于成长的电影，背景设定在一战前夕的布达佩斯。 Age: 44 The 43-year-old woman was placed on a 12-month good behaviour bond and banned from owning animals. Japan, ranked No. 5 overall, is the top performing Asian country. It ranks No. 5 in Movers and No. 1 as the most forward-looking country. 卡尔还表示：“就算没有厄尔尼诺现象，去年气温也有可能创纪录，但厄尔尼诺现象让高温更加极端。” 为什么这么说呢？只需想想最高法院对同性婚姻问题做出裁决之后人们越来越强烈的怒火，想想人们围绕堕胎、奥巴马医改、枪支管制、食品券、共和党州长新推的选民压制等问题越来越强烈的怒火，另外还有保守派和茶党顽固不化，力争推翻一切立法并加强财政紧缩。 美国各州对特斯拉大献殷勤，希望在其计划投资50亿美元兴建的大型锂电池工厂选址中胜出。这家工厂有可能解决多达6500人的就业。加利福尼亚州就正在与内华达、亚利桑那、新墨西哥和德克萨斯等州展开竞争，而吸引该厂落户的条件据说是要给予5亿美元的支持。 INDOORS: This house was completed around 1848 and last updated in 2008. The front door has a transom and sidelights of red glass etched with a leaf motif. The first floor has a large living room with crown molding and two fireplaces, one of which warms the formal dining area. Off the living room is a family room with raised wall paneling, a wet bar and another dining area. French doors open to a slate patio. Several rooms have views of Little Narragansett Bay. 3. 向他人学习。 The number of country rankings published this year rose to 42, up from 38 last year. The newly featured countries are Argentina, Mexico, Pakistan and Romania. 拉杜卡(Rocco LaDuca)是纽约州尤蒂卡市(Utica)《观察家快报》(Observer-Dispatch)报道犯罪和法院新闻的记者。他说，之所以选择做记者，一定程度上是源于他和祖母读报的美好记忆。 他说道：“我们也在见证一个有关多样化的积极的发展。在过去，大多数中国企业的专利申请主要集中在信息通信技术领域，但是现在有越来越多的专利申请出现在了发动机、泵体、涡轮机、汽车行业以及生物技术等领域。” Some 18.1 million people, for example, want a good full-time job but can't find one, an unusually high number 5 1/2 years into a recovery. And despite a sharp decline in the number of people out of work six months or longer, that figure is still higher than at any time before the 2007-09 recession.
Of special interest in the appearance of objects is their color as it can set the objects apart from the environment and might signal their use or condition. For example, a slightly brownish tint on an apple signals that is rotten. Law-Smith et al. (2006) found that there are visual cues in female faces that are indicative of high estrogen levels and which are associated with ratings of femininity, attractiveness, and healthiness. Law-Smith et al.'s facial images suggest that a slightly reddish tint is one of those cues. Humans have four different types of photoreceptors that allow them to see light with wavelengths between roughly 350 nm (violet) and 750 nm (red). Three photoreceptors are associated with color vision whereas the fourth photoreceptor is associated with ‘night vision’. Wyszecki and Stiles (1982/2000) give an elaborate overview on color science, as well as a wealth of quantitative data on the subject.
In its decision to not boost its monetary stimulus efforts, the Bank of Japan noted industrial production was one area where the economy was just puttering along. Certainly, there were other parts of the economy, such as the labour market, that were doing much better. 2、冷静自若。007总是很平静。（对男女来说都有用）。即便是在死到临头的时候，也很冷静。这就是性感啊。邦德从不慌张失措。你没见过邦德腿发软手发抖吧。他讲话时语速慢而谨慎，从不乱阵脚。这些都是极富魅力的品质，遭遇劲敌面不改色-这很容易让女人心动不已。他从不向女人表白个不停，就让她们猜不透，搞不懂，这样更加有吸引力。邦德不常微笑也为他的性感加分，因为有幸福感的男人吸引不了女人。007的肢体语言很强势，阳刚血性，从不畏惧；007从不喋喋不休，让他更加优雅；007从不懒散，挺拔的体姿不仅增加自信心，还有力量感，看起来更强壮（身着燕尾服与恶棍搏斗看起来更有档次）。 More importantly, their inventions may even eventually be turned into products that benefit mankind. 2.室内类比赛项目 Simply put, bladeless fans are fans without blades. They work by sucking in air at their base and then blowing them out through several holes in their ring. The fan is reported to have been invented by James Dyson, who calls it the "Air Multiplier." Just like the flying jetpack, it earned a spot in Time's list of notable inventions of 2009. And just like the jetpack, it was not the first of its kind. The first bladeless fan was actually patented in 1981 by a Japanese company called Tokyo Shiba Electric. Although Tokyo Shiba's bladeless fan was never manufactured, James Dyson's initial design of a bladeless fan design looked so similar to that of Tokyo Shiba Electric that the patent office refused to grant him a patent. The patent granted to Tokyo Shiba had already expired, but the patent office still required something substantially different before it could grant a new patent to James Dyson. Dyson's patent manager, Gill Smith, did not deny the similarities between both bladeless fans but said the difference between them was the "technology." n. 运输、运输工具；(常用复数）强烈的情绪（狂喜或狂怒 1.Under no circumstances should you ask your taxi driver how excited he is about having the Olympics in London this summer. It's not that he will be reluctant or embarrassed to offer a personal opinion on the matter. That is not the problem at all. 这些人当中，有些人会借助另一些问题表达他们的忧虑：贸易、犯罪、毒品战争、边境控制、对伊斯兰恐怖主义的恐惧。诚然，这些问题都很重要，也为许多人带来了真切的恐惧，但是它们已经变成一种方式，公众借助这些问题来讨论社会变革对于占多数的白人群体的影响。 这意味着投资者正为特斯拉的未来前景投下重注，出价要远远高于对其他豪车厂商实际表现的评估。梅塞德斯-奔驰（Mercedes-Benz）的制造商戴姆勒（Daimler）去年售出了超过250万辆车，市值约为850亿美元。所以，尽管戴姆勒的销量是特斯拉的70多倍，但它的市值还不到特斯拉的3倍。 Chinese telecommunications giant Huawei filed a notable 2,390 patents, which was the second-largest filing by a company globally, after Philips with 2,568 patents. 《剧集人生》(Episodes)：映时频道的这部喜剧经常被忽视，它讲述的是两位被困在好莱坞的英国电视编剧在为马特·勒布朗(Matt LeBlanc)创作电视剧时遇到的困惑。勒布朗在剧中饰演他自己，演得很精彩。以娱乐业为背景的电视剧很少能保持最初的巧妙构思，但这部剧的第三季比前两季还要精彩。 Faucher说“在2015年年底我们的失业率大致会处在5%到5.5%之间，而且会让我们更加实际的感受到这一点”。 反腐力度将会被加强。2014年中国反腐调查案件将会从如今的14万件，增加到超过20万件。这将使得中国更强大。 如果反腐能够成功，将会使中国更关注于做事，而不是搞人事关系。 据中国海关总署公布的统计数据显示，2016年中德外贸总额达到了9991亿元人民币（约合1453亿美元），同比2015年增长了2.6个百分点。 Not only does its small cohort of about 50 allow the school to select highly experienced participants, it also creates a strong bond between them. Only three Hollywood productions, 'Furious 7', 'Avengers: Age of Ultron', and 'Jurassic World', made it into the top 10 at the Chinese box office in 2015. But back to TextPride. Wray and O’Brien saw the way users eagerly engaged with their branded emojis, and believed advertisers appreciated the convenience of using one vendor to get many different messaging apps. But they realized that that was only half of the business. For certain established brands like sports teams, people will pay for stickers. But other, unknown brands would pay just to be included. 立场：和员工分享300万美元奖金
The three light sources that were used to measure the CIE color matching functions were quite arbitrarily chosen. In fact one can perform the same procedure with three different light sources as long as they are sufficiently far apart in wavelength or color. It is relatively straightforward to calculate the correspondence between sets of color matching functions made with different light sources. I have plotted the CIE color matching functions in Figure 1.6A. The points of monochromatic lights form a continuous curve in the space spanned by the three light sources. A ‘color cone’ can be constructed by connecting the origin with all monochromatic points. All possible colors that can be perceived have a corresponding coordinate within the color cone. Usually, a cross-section is made through the color cone at which the intensity of the light is perceived as constant, as in Figure 1.6B. In Figure 1.6B all data points lay on a plane. This plane forms the CIE (x, y)-chromaticity diagram that might be familiar to the reader. Colors can be described with their coordinates in this plane, along with their intensity. Note that some colors, namely the purples, are not on the color-matching curve. There are no wavelengths that correspond to this color, because they can only result from a combination of a ‘reddish’ and a ‘bluish’ wavelength. Purples can be found on what is called the purple plane, the flat plane in Figure 1.6A, or purple line, the straight line in Figure 1.6B, in case of a chromaticity diagram. This plane closes the gap between the red side and blue side of the color cone.
The chromaticity coordinates for any light source can easily be found by multiplying the color matching functions with the spectrum of the light source. The color matching functions can, for example, be obtained from the Color and Vision Laboratories of the Institute of Ophthalmology at the University College London (http://www.cvrl.org). It is possible that different spectra yield the same chromaticity coordinates. The colors of these light sources are thus the same. This phenomenon is known as metamerism. Usually, objects with metamer colors can easily be distinguished by looking at them through a colored filter or by shining light of a different spectrum on them. For example, a trick that is sometimes employed by the colorblind to distinguish red and green is to view them through a red filter. Red and green are metamer colors for the colorblind. Viewing a red object through a red lens does not change its intensity, but a green light that is viewed through a red filter turns to black.
当她向经理咨询的时候，凯说，当他们的员工开始不经常和他们讲话，无论是更新工作内容，询问意见还是仅仅打个招呼，他们中的许多人都能警觉地察觉到一些事情。正如凯总结地那样：“你开始不做那些你日常维持社交关系的事情了。” 保罗·乔治，克里斯·保罗，卡梅罗·安东尼，戈登·海沃德，吉米·巴特勒，德里克·罗斯，保罗·米尔萨普，J·J·雷迪克，埃里克·布莱索，德怀特·霍华德……自去年以来，换了东家的球员名单还在不断增加。 But many foresee an economic collapse, arguing that a prolonged eurozone crisis coupled with a property bubble could render vast swaths of Chinese industry unprofitable. This would reveal hidden financial vulnerabilities and feed a downward spiral. Others believe that Beijing has ample resources to avoid a crisis, but argue that, with a growth model based on infrastructure and land sales, and with exchange and interest rates rigidly controlled, it may not have all the necessary tools at its disposal. 最佳二人组：汤普森广场 Though its campuses often steal the benefits spotlight -- with their outdoor sports facilities, free food and more -- there's a more morbid perk that should certainly be noted. If a U.S. Googler passes away while working for the tech giant, the employee's spouse or domestic partner receives 50% of the deceased's salary, no matter how long or short his tenure, every year for the next decade. 考夫曼和同事加雷思?哈里斯(Gareth Harris)发现，居住在那些人种快速多样化地域的英国白人更倾向于投给右翼的英国国家党(British National Party)。宾夕法尼亚大学政治学教授丹尼尔?霍普金斯(Daniel Hopkins)在美国发现了相似的民族变化导致反移民政策的规律。 4.Avoid micromanaging The base hopes to keep up public awareness of pandas and the necessity of conservation of their natural habitats while Increasing the wild population by reintroducing individuals into areas in China where populations have declined.
Not all colors can be made given a certain illumination spectrum. If there is no light in the red part of the spectrum, it is impossible to make an object look red, whatever its spectral reflection function. For example, the color of an object is very different in daylight than under the illumination of yellow streetlights. In fact, since sodium streetlights are monochromatic, there are no colors any more! All light that comes into the eye is of the same wavelength, irrespective of the material that has reflected it to the eye; only the intensity of the light differs. The casual observer might not even notice the absence of color under these conditions though, because there is still a lot of variation in light intensity. Given a certain illumination spectrum, it is possible to calculate all possible colors that can be made from shining this light on a surface. The resulting colors are called object colors. An object color is the color that the observer identifies as the color of an object. Object colors can thus, depending on the spectral composition of the illumination, take on different values. The object colors for a given illumination spectrum fill only a part of the color cone. The set of object colors thus fills a different volume, often called ‘color solid’, for each specific illumination spectrum. The volume is filled with all colors that can result from all possible reflectance functions and given a certain illumination spectrum. I have created such a color solid in Figure 1.6C. I have taken a standard illuminant, namely ‘CIE-D65’, and calculated all colors that can result under that illumination. The CIE has specified several standard illuminants for this purpose.
There are many systems to order different object colors. I will briefly mention one particularly popular model, namely the Munsell Color system. The Munsell system orders object colors on three dimensions namely: Luminance; hue; and saturation. Luminance is a value between black and white. Hue can be described as ‘red’, ‘blue’, ‘purple’, and so on. Saturation is the amount of hue as opposed to being gray. Pastel colors, for example, have a low saturation. The system is composed of a set of differently colored chips that can be arranged in a solid, much like in Figure 1.6C. The chips are chosen such that their discriminability increases in equal steps. The Munsell color system does not take into account how colors of materials change over viewing, illumination angle, and spectral composition of the light source. Calibrated chip sets for the Munsell are commercially available. More detail on the CIE color matching functions, the Munsell color system, etc., can be found in Wyszecki and Stiles (1982/2000).
Object colors as discussed so far do not form the entire story though. There are a few restrictions. First, the BRDF is dependent on the wavelength of illumination. A striking example is the Compact Disc. Light with the same angle of incidence but different wavelengths is reflected in different directions on a Compact Disc. A full description of the color of an object therefore involves the viewing and illumination directions as well. Secondly, the perceived color of objects also depends on the color of the environment. The chromaticity coordinates and the Munsell system is only valid when the object or light is viewed against a gray background. I will address this further in Section 3.2. Obviously, this has important consequences for the product designer, as the typical illumination and viewing conditions in which the product is going to be sold or used must be taken into account.