Quantitative Characteristics of Debit Age from Heat Treated Chert

Abstract

Quantitative results of knapping of some Texas cherts, before and after thermal alteration, are presented. Improvements in knapping qualitites of these cherts after heat treating are discussed on an empirical basis.     

模拟打制实验及其在丁村角页岩石器研究中的应用

模拟打制是史前考古研究中的重要实验考古方法之一,对于正确认识考古标本的类型和技术、解读当时人类的认知水平和知识积累具有不可取代的作用。本文简要回溯了模拟打制实验的发展史,并评述其应用现状。模拟打制实验在欧美有较长的发展与应用历史,但最终趋向了不同的发展方向。传统的模拟打制实验研究在欧洲得到了更加深入的继承和发展,而美国在上世纪90年代后期逐渐发展起了以定量控制、数理统计为核心的实验方法。本文以近期在山西丁村开展的角页岩模拟打制实验为例,介绍传统的模拟打制实验的基本流程和内容,包括实验的内容设计、实施及记录和分析等。本次实验结果肯定了硬锤锤击技术在丁村角页岩石核剥片和修理中的广泛应用,并在一定程度上否定了以往对使用碰砧法的推测。文章最后对模拟打制实验存在的问题和应用前景作了讨论和展望。     

陶寺遗址石制品复制实验与磨制工艺

本文主要介绍了陶寺遗址石制品复制实验的目的、方法、过程和结果,其中,过程部分主要介绍了磨制石器的复制。结果部分主要是通过实验考察了陶寺遗址磨制石器生产所需的几种工艺,以及这些工艺的操作所需的工具、时间等因素。文章认为,陶寺遗址磨制石器的制作过程简单,一般只需打片和磨两个步骤。磨比较简单易操作,只是比较耗费时间;而打片相对于打制石器来讲,要简单很多。因此,陶寺遗址磨制石器的制作工艺总体来讲比较简单易操作。     

siRNA对SARS冠状病毒复制的抑制作用

为探讨siRNA在哺乳动物细胞中对SARS冠状病毒复制的抑制作用,针对BJ0 1株SARS冠状病毒复制酶基因(Pol)和刺突蛋白基因(S) ,设计4个siRNA ,并构建相应的siRNA表达载体及克隆细胞系.利用间接免疫荧光法及实时定量反转录PCR法,检测所设计的siRNA对SARS冠状病毒复制的抑制作用.结果表明,针对Pol基因的siRNA(psOe)在Vero细胞中可阻断BJ0 1株SARS病毒RNA的复制及其蛋白的表达.该结果为深入阐明SARS冠状病毒的致病机理及探讨SARS病毒防治新途径奠定了基础.     

Classification of Object Size in Retinotectal Microcircuits

1. Download : Download high-res image (362KB)
2. Download : Download full-size image

     

Small but Mighty: Cell Size and Bacteria

Our view of bacteria is overwhelmingly shaped by their diminutive nature. The most ancient of organisms, their very presence was not appreciated until the 17th century with the invention of the microscope. Initially, viewed as “bags of enzymes,” recent advances in imaging, molecular phylogeny, and, most recently, genomics have revealed incredible diversity within this previously invisible realm of life. Here, we review the impact of size on bacterial evolution, physiology, and morphogenesis.Humanity has always experienced the impact of microorganisms, most obviously through their ability to cause devastating disease. For the vast majority of human history, we were unaware of their presence, much less the fundamental microbial processes to which we owe our existence: from the production of energy by our ancient bacterial endosymbionts (the mitochondria) to the generation of oxygen in our atmosphere. Despite their astounding global abundance (∼10³⁰ cells) and their substantial contribution to the total biomass of planet earth (Whitman et al. 1998; Kallmeyer et al. 2012), our inability to see these tiny life forms shrouded their nearly limitless diversity in mystery. It was not until the 17th century, with the careful observations and reports of Anton van Leeuwenhoek, that we became aware of this previously invisible world on and around us. Today, we know that there are more bacteria living in our intestinal tract than stars in the Milky Way galaxy (and that they far outnumber all the people who have ever lived). We also know now that we thrive because of their metabolic support. Although less than 1% of bacteria can be cultured readily in the laboratory (Amann et al. 1995), the biochemical versatility among these tiny creatures exceeds that of the plants, animals, and fungi combined (Pace 1997).Anton van Leeuwenhoek’s illustrations in a letter to the Royal Society of London in the late 17th century provide one of the earliest records of bacterial cell form (Dobell 1960). Viewed through a single lens, Leeuwenhoek pioneered studies of the human microbiome, describing motile bacilli, cocci, and spirochetes he found in scrapings taken from between his teeth (and the teeth of others). This triumph was made possible by incomparable curiosity, lens construction, and exceptional lighting. The simple cellular structure and glassy nature of most unstained bacteria viewed with a light microscope generated little interest in bacterial cell biology with the exception of objects of unusual contrast, such as endospores described by Robert Koch and the wonderfully colorful and large cyanobacteria. The bacterial nature of the latter was itself only appreciated late in the 20th century (Oren 2004). For the most part, bacteria were viewed as primitive “bags of enzymes” until the 1990s, when the complexity of bacterial subcellular structure and regulators of cell reproduction finally began to emerge. Tools and reagents developed for eukaryotic cell biology (e.g., stains for DNA, membranes, and fluorescent protein tags), once applied to bacterial cells, revealed astonishing insights including the specific and even dynamic localization patterns of proteins, and the accuracy of chromosome organization.     

Maternal Size and Age Shape Offspring Size in a Live-Bearing Fish,Xiphophorus birchmanni

Many studies of offspring size focus on differences in maternal investment that arise from ecological factors such as predation or competition. Classic theory predicts that these ecological factors will select for an optimal offspring size, and therefore that variation in a given environment will be minimized. Yet recent evidence suggests maternal traits such as size or age could also drive meaningful variation in offspring size. The generality of this pattern is unclear, as some studies suggest that it may represent non-adaptive variation or be an artifact of temporal or spatial differences in maternal environments. To clarify this pattern, we asked how maternal size, age and condition are related to each other in several populations of the swordtail Xiphophorus birchmanni. We then determined how these traits are related to offspring size, and whether they could resolve unexplained intra-population variation in this trait. We found that female size, age, and condition are correlated within populations; at some of these sites, older, larger females produce larger offspring than do younger females. The pattern was robust to differences among most, but not all, sites. Our results document a pattern that is consistent with recent theory predicting adaptive age- and size-dependence in maternal investment. Further work is needed to rule out non-adaptive explanations for this variation. Our results suggest that female size and age could play an under-appreciated role in population growth and evolution.     

Size, Age and Demography of Metamorphosis and Sexual Maturation in Fishes

Understanding what determines the timing of transitions betweenlife-history stages in fishes is crucial to an understandingof their demography. Most theoretical treatments assume thatthese transitions are age dependent, but evidence accumulatingfrom a variety of organisms indicates that size is an importantvariable also. In the starry flounder, Platichthys slellatus(Pallas),the onset of metamorphosis is more closely related to size thanage. In the platyfish, Xiphophorus maculatus (Günther),the onset of sexual maturation depends on both size and age.I compare these results with those reported for other organisms,and outline the expected ecological correlates of age- and sizedependenttransitions between life history stages in general.     

Classification of Orchidaceae in the Age of DNA data

Summary.  The relationships of orchid tribes and subtribes are discussed in the light of recent DNA studies. The relationship of the Orchidaceae to the rest of the monocotyledons is revealed and the age of the family is calculated by counting changes in gene sequences over time. A summary cladogram of orchid relationships based on published DNA studies is given.     

Size Estimates in Ebbinghaus Illusion in Adults and Children of Different Age

Psychophysical experiments were performed with the participation of 297 subjects (adults and 6- to 17-year-old children and adolescents). Perception of the size of a central stimulus surrounded by other stimuli was studied. Subjects had to estimate the size of a circle with a diameter of 22 angular min, which was surrounded by four similar figures with a diameter of either 11 or 44 angular min at a distance of either 11 or 33 angular min. The misperception of the stimulus size was dependent on the subject's age, the distance between the circles, and the size of the flanking circles. The smaller flanking circles located at any distance produced size underestimation in younger children; these circles led to size overestimation in case of their location at a short distance in most adults and adolescents. The larger flanking circles produced underestimation in all age groups, but, in adults, unlike children, this illusion decreased with increasing distance. The illusion mechanism and its possible connection with selective attention are discussed.     

Tactile Spatial Acuity in Childhood: Effects of Age and Fingertip Size

Tactile acuity is known to decline with age in adults, possibly as the result of receptor loss, but less is understood about how tactile acuity changes during childhood. Previous research from our laboratory has shown that fingertip size influences tactile spatial acuity in young adults: those with larger fingers tend to have poorer acuity, possibly because mechanoreceptors are more sparsely distributed in larger fingers. We hypothesized that a similar relationship would hold among children. If so, children’s tactile spatial acuity might be expected to worsen as their fingertips grow. However, concomitant CNS maturation might result in more efficient perceptual processing, counteracting the effect of fingertip growth on tactile acuity. To investigate, we conducted a cross-sectional study, testing 116 participants ranging in age from 6 to 16 years on a precision-controlled tactile grating orientation task. We measured each participant''s grating orientation threshold on the dominant index finger, along with physical properties of the fingertip: surface area, volume, sweat pore spacing, and temperature. We found that, as in adults, children with larger fingertips (at a given age) had significantly poorer acuity, yet paradoxically acuity did not worsen significantly with age. We propose that finger growth during development results in a gradual decline in innervation density as receptive fields reposition to cover an expanding skin surface. At the same time, central maturation presumably enhances perceptual processing.     

Interaction of Human Replication Protein A with DNA Duplexes Containing Gaps of Varying Size

Replication protein A (RPA) is a heterotrimeric protein that has high affinity for single-stranded (ss) DNA and is involved in DNA replication, repair, and recombination in eukaryotic cells. Photoaffinity modification was employed in studying the interaction of human RPA with DNA duplexes containing various gaps, which are similar to structures arising during DNA replication and repair. A photoreactive dUMP derivative was added to the 3" end of a gap-flanking oligonucleotide with DNA polymerase , and an oligonucleotide containing a 5"-photoreactive group was chemically synthesized. The 5" end predominantly interacted with the large RPA subunit (p70) regardless of the gap size, whereas interactions of the 3" end with the RPA subunits depended both on the gap size and on the RPA concentration. Subunit p32 was mostly labeled in the case of a larger gap and a lower RPA concentration. The results confirmed the model of polar RPA–DNA interaction, which has been advanced earlier.     

石制品使用微痕多阶段成形轨迹的实验研究

石制品微痕是进行石器功能研究、了解史前人类行为模式的重要考古证据之一。本文在以往实验研究的基础上, 设计并开展多阶段燧石制品"刮骨"微痕实验, 分阶段详细、直观地记录石制品刃缘使用微痕的最初形成与发展动态。实验研究表明, "刮骨"使用微痕迹随着使用时间长度的递增发生复杂的动态变化, 使用微痕的发展与使用时间之间并非简单的正函数关系。片疤破损自开始在一定时间段内呈连续发生状态, 随后停止发展, 是确认石制品是否经过使用的良好指示。磨圆表现出由少到多、由弱及强的逐渐发育过程, 可以反映石制品的使用时间和强度, 也是判断使用微痕的重要参考依据。     

Relation between Age of Onset of Obesity and Size and Number of Adipose Cells

The size and number of adipose cells in obese children and adults were compared with control data. An increase in adipose cell size was found in all the obese subjects. The total number of adipose cells was increased in those children who had become obese already by the age of 1 year and in those adults who dated their obesity to childhood.     

Long-Term Survival of Individuals Born Small and Large for Gestational Age

Background

Little is known on long-term survival and causes of death among individuals born small or large for gestational age. This study investigates birth weight in relation to survival and causes of death over time.

Methods

A national cohort of 1.7 million live-born singletons in Denmark was followed during 1979–2011, using the Danish Civil Registration System, the Medical Birth Registry and the Cause of Death Registry. Cox proportional hazards were estimated for the impact of small (SGA) and large (LGA) gestation weight and mortality overall, by age group and birth cohort.

Results

Compared to normal weight children, SGA children were associated with increased risk of dying over time. Though most of the deaths occurred during the first year of life, the cumulative mortality risk was increased until 30 years of age. The hazard ratios [HR] for dying among SGA children ages <2 years were: 3.47 (95% CI, 3.30–3.64) and 1.06 (95% CI, 0.60–1.87) in 30 years and older. HR for dying among SGA adults (20–29 years) were: 1.20 (95% CI, 0.99–1.46) in years 1979–1982 and 1.61 (95% CI, 1.04–2.51) in years 1989–1994. The SGA born had increased risk of dying from infection, heart disease, respiratory disease, digestive disease, congenital malformation, perinatal conditions, and accidents, suicide, and homicide. Individuals born LGA were associated with decreased mortality risk, but with increased risk of dying from malignant neoplasm.

Conclusions

Survival has improved independently of birth weight the past 30 years. However, children born SGA remain at significantly increased risk of dying up till they turn 30 years of age. Individuals born LGA have lower mortality risk but only in the first two years of life.     

Template RNA Length Determines the Size of Replication Complex Spherules for Semliki Forest Virus

The replication complexes of positive-strand RNA viruses are always associated with cellular membranes. The morphology of the replication-associated membranes is altered in different ways in different viral systems, but many viruses induce small membrane invaginations known as spherules as their replication sites. We show here that for Semliki Forest virus (SFV), an alphavirus, the size of the spherules is tightly connected with the length of the replicating RNA template. Cells with different model templates, expressed in trans and copied by the viral replicase, were analyzed with correlative light and electron microscopy. It was demonstrated that the viral-genome-sized template of 11.5 kb induced spherules that were ∼58 nm in diameter, whereas a template of 6 kb yielded ∼39-nm spherules. Different sizes of viral templates were replicated efficiently in trans, as assessed by radioactive labeling and Northern blotting. The replication of two different templates, in cis and trans, yielded two size classes of spherules in the same cell. These results indicate that RNA plays a crucial determining role in spherule assembly for SFV, in direct contrast with results from other positive-strand RNA viruses, in which either the presence of viral RNA or the RNA size do not contribute to spherule formation.