New age constraints on the Middle Stone Age occupations of Kharga Oasis, Western Desert, Egypt

Spring-deposited carbonate rocks, or tufas, exposed along the flanks of the Libyan Plateau near Kharga Oasis, Western Desert, Egypt, can provide a directly datable stratigraphic context for Middle Stone Age/Middle Paleolithic (MSA/MP) archaeological material, if such material can be found in situ within tufa strata. Two such localities (Mata'na Site G and Bulaq Wadi 3 Locus 1) described by Caton-Thompson were revisited and sampled for uranium-series analysis. At Mata'na Site G (KH/MT-02), Middle Stone Age ("Upper Levalloisian") material is underlain by tufa with a uranium-series age of 127.9+/-1.3 ka, and overlain by tufa with an age of 103+/-14 ka. At Bulaq Wadi 3 Locus 1, a uranium-series age of 114.4+/-4.2 ka on tufa capping a small collection of Middle Stone Age artifacts also provides a minimum age constraint on that material. Tufa underlying an MSA workshop (KH/MD-10) indicates that this assemblage, characterized by use of several Levallois reduction methods, was deposited after approximately 124 ka. Furthermore, uranium-series ages averaging approximately 133 ka on a Wadi Midauwara tufa (WME-10) without associated archaeological material suggest that one period of spring flow in the region began during the Marine Isotope Stage 6/5e transition, prior to the warmest portion of the last interglacial period. The dated archaeological material suggests that the distinction that has been identified between Nubian and non-Nubian complexes in the Nile Valley may hold for the Western Desert, although local complexity has yet to be fully described.     

Quasi-Local Competition in Stage-Structured Metapopulations: A New Mechanism of Pattern Formation

A central question of ecology is what determines the presence and abundance of species at different locations. In cases of ecological pattern formation, population sizes are largely determined by spatially distributed interactions and may have very little to do with the habitat template. We find pattern formation in a single-species metapopulation model with quasi-local competition, but only if the populations have (at least) two age or stage classes. Quasi-local competition is modeled using an explicit resource competition model with fast resource dynamics, and assuming that adults, but not juveniles, spend a fraction of their foraging time in habitat patches adjacent to their home patch. Pattern formation occurs if one stage class depletes the common resource but the shortage of resource affects mostly the other stage. When the two stages are spatially separated due to quasi-local competition, this results in competitive exclusion between the populations. We find deep similarity between spatial pattern formation and population cycles due to competitive exclusion between cohorts of biennial species, and discuss the differences between the present mechanism and established ways of pattern formation such as diffusive instability and distributed competition with local Allee-effects.     

Effects of aging on functional properties of caprine milk made into Cheddar- and Colby-like cheeses

The effects of cheese milk obtained at three times during lactation (weeks 4–5, 12–15, and 21–23) and cheese storage (up to 16 or 24 weeks) on meltability, sliceability, and color changes upon heating (232 °C for 5 min, high baking temperature, HT, or 130 °C for 75 min, low baking temperature, LT) of caprine milk cheeses were evaluated. The cheeses were manufactured from milk from Alpine goats and based on the procedures of Cheddar and Colby cheese manufacture. In Cheddar-like cheese, the sliceability (force required to slice sample) was at its highest when the cheese was made with milk from weeks 12–15 into lactation. Color change was variable although it tended to be lowest in cheese made at weeks 4–5 into lactation. In Colby-like cheeses, meltability was at its highest and sliceability was very poor (after 8 weeks of aging) when made with milk obtained later in lactation. Color changes were variable at the two different baking temperatures. As expected during aging, the meltability of the cheeses increased and the force required to slice the cheeses decreased with the significant changes occurring within the first 16 weeks for Cheddar-like and the first 8 weeks for Colby-like cheeses. The color changes upon heating were variable for aged Cheddar-like cheeses and did not change significantly for aged Colby-like cheeses. Color changes were highly correlated with proteolysis occurring during storage. Cheese milk obtained at different times of lactation and aging of the cheese impact the functional properties of caprine milk cheeses and will affect their optimal utilization.     

Moms are better nurses than dads: gender biased self‐facilitation in a dioecious Juniperus tree

Questions: Can gender of nurse plants affect regeneration patterns and spatial population structure? Is there a seed‐seedling conflict in the regeneration process? What factors are responsible for the clumped spatial population structure observed for adult trees? Location: Mediterranean cold semi‐arid high mountains in Spain. Methods: The spatial pattern of adult Juniperus thurifera trees was studied by means of Ripley's K‐analysis. χ² analyses were used to test for natural seedling frequency in each of three main microhabitats: (1) under female and (2) male tree canopies and (3) in open interspaces. The observed pattern was explained experimentally by studying seed and seedling survival for two years. Survival probabilities were calculated across life stages for each of three main microhabitats. Results: Adult J. thurifera trees were aggregated in space. Most seedlings were found underneath female J. thurifera trees. Experimental studies demonstrated that from seed dispersal to seedling survival all life stages showed the same positive or negative trend within a given microhabitat, indicating stage coupling and no seed‐seedling conflicts. Attraction of frugivo‐rous birds by reproductive female junipers and improvement of environmental conditions beneath tree canopies were the main factors responsible for the variation in seedling density among microhabitats; highest underneath female trees and lowest in open interspaces. Conclusions: In dioecious species, the gender of nurse plants can significantly determine the spatial population structure. In J. thurifera forests, facilitation beneath female trees occurs among all life stages without any sign of seed‐seedling conflict. The most critical factors shaping the spatial population structure were directed seed dispersal and environmental amelioration beneath female conspecific trees.     

贵州松桃黄莲寒武系都匀阶杷榔组三叶虫地层划分及意义

贵州松桃县黄莲村西的黄莲剖面杷榔组厚417.8m,主要由深灰色钙质泥岩组成,岩性与湘西、黔东杷榔组基本相似,除底部38m未见三叶虫外,以上均含有三叶虫,由下而上可分为2个三叶虫带,下为Oryctocarella duyunensis带(38-83m),化石较少;上为Oryctocarella duyunensis-Arthricocephlus chauveaui组合带(83 m以上)。除Arthricocephlus chauveaui外,还含有A.xinzhaiheensis,Oryctocarella duyunensis,O.sibirica?,O.balangensis,Duyunaspis duyunensis,Changaspis elongata及Redlichia (Pteroredlichia)murakamii。与剑河交榜潜在的寒武系第四阶国际层型剖面下部2个三叶虫带Oryctocarella duyunensis-Arthricocephlus chauveaui组合带及Oryctocarella duyunensis带完全相同,也可和格陵兰北部Freachen land及Peary land等地Henson Gletscher组对比。黄莲剖面是潜在的寒武系第四阶国际层型剖面剑河交榜杷榔组剖面的良好辅助剖面。     

动态对比增强磁共振成像在鼻咽癌分期中的应用价值

目的:分析动态对比增强磁共振成像(DCE-MRI)在鼻咽癌分期中的应用价值。方法:选取2016年6月至2018年4月我院经病理证实的初诊鼻咽癌患者104例为研究对象,均行DCE及扩散加权成像(DWI)检查,比较不同鼻咽癌分期患者的DCE-MRI定量参数[转运常数(Ktrans)、血管外细胞外间隙体积百分数(Ve)、速率常数(Kep)、容积分数(f PV)]及表观扩散系数(ADC)值,分析各DCE-MRI参数与临床分期的相关性,并评估DCE-MRI对鼻咽癌分期的诊断价值。结果:随总分期增加,鼻咽癌患者Ktrans、Ve增加,且Ve随T分期增加而增加,M1分期者Ktrans、Ve大于M0分期者(P0.05),不同N分期患者各DCE-MRI参数比较差异无统计学意义(P0.05),Kep、f PV在各分期中比较差异也无统计学意义(P0.05);随总分期增加,鼻咽癌患者ADC值减少(P0.05);Spearman相关分析发现,鼻咽癌患者Ktrans与总分期、M分期呈正相关,Ve与总分期、T分期呈正相关,ADC值与总分期呈负相关(P0.05);各参数中,Ktrans诊断鼻咽癌总分期的曲线下面积(AUC)最大,为0.925,Ktrans诊断鼻咽癌早期(Ⅱ期)、晚期(Ⅲ期与Ⅳ期)的AUC分别为0.909、0.921,均较ADC(AUC=0.864、0.815)高。结论:DCE-MRI在鼻咽癌临床分期中有较高应用价值,其中Ktrans的诊断效能最好且高于DWI诊断,肿瘤分期越高,Ktrans越大,可作为肿瘤分期的一个指标。     

非自治阶段结构与时滞捕食模型的持久性和周期解

讨论了一类非自治阶段结构带有消化时滞的两种群捕食模型,其中只有一个种群有阶段结构,本文得到了这个系统能够持久生存的条件．进一步,如果这个系统是周期系统我们证明了在一定条件下系统存在唯一的全局渐近稳定的正周期解。     

中国宜昌王家湾晚奥陶世五峰组几丁虫的初步研究

中国宜昌王家湾北剖面已被提名为奥陶系赫南特阶的全球候选层型剖面。为此著者分析了王家湾地区,特别是王家湾南和王家湾小河边奥陶—志留系间相关地层共20个层位的几丁虫样品。初步研究的结果表明,王家湾赫南特阶之下,相当奥陶纪第6个阶顶部,即五峰组中部产出的几丁虫与美国内华达中部Vnini河谷以及加拿大极区Cape Mannig的Ordochitina nevadensis 和Nevadachitina vininica 几丁虫带的分子可以进行对比。     

我国石炭系达拉阶标准剖面的牙形刺

本文详细地研究了石炭系达拉阶标准(或层型)剖面,即贵州盘县达拉寨剖面的牙形刺。在标准剖面达拉阶上部,即相当于先前的有孔虫Fusulinella—Fusulina带的层位,产牙形刺Idiognathodus podolskensis,I．delicatus,I．magnificus,I．obliquus,I．claviformis,Streptognathodus cancellosus和S．parvus等,并自下而上可划分为Idiognathodus podolskensis带和Streptognathodus cancellosus带,前者相当于有孔虫Fusulina pakhrensis-Pseudostaffella paradoxa带下部及Fusulina lanceolata-Fusulinella uozhgalensis带,后者则与Fusulina pakhrensis Pseudostaffella paradoxa带上部和Fusulina cylindrica-F．quasifusulinoides带相当,并可与东欧的莫斯科阶(Moscovian)上部对比。标准剖面达拉阶下部,即相当于有孔虫Profusulinella带的层位未见牙形刺化石,但根据贵州罗甸纳水剖面的资料,有孔虫Profusulinella带之底在牙形刺Diiplognathodus ophanus-D．ellesmerensis带之中通过,因此在罗甸纳水剖面,达拉阶之底比莫斯科阶之底要稍高些。纳水剖面的有孔虫来自台地垮塌的沉积,这类沉积物是不连续的,因此其有孔虫带与牙形刺带的关系并不十分可靠。但总的来看,我国的达拉阶仍大致可与莫斯科阶相对比。