Corrosion casts as a method for investigation of the insect tracheal system

Summary The tracheal systems of five insect species (two species of ants, worker bee, housefly and the cabbage butterfly) have been studied by scanning electron microscopy of corrosion casts. This technique, which is commonly used for the investigation of vertebrate vasculature, is adapted to demonstrate the ultrastructure of the insect respiratory organ. The problem of filling a blind ending system was solved by injecting the resin Mercox into the evacuated tracheae through a thoracal spiracle. After polymerization of the resin, the tissue was digested enzymatically and chemically. The three-dimensional structure of the tracheal system was investigated by scanning electron microscopy. The technique used here displays for the first time the complex morphology of the entire tracheal system in fine detail, especially the structure of spiracles, airsacs, tracheae and tracheoles. Smooth-walled terminal tracheoles show up in flight muscles. The finest tracheoles that could be identified have diameters of approximately 70 nm. This approaches the finest tracheoles portrayed by transmission electron micrographs.     

Vascular morphology of the bovine spermatic cord and testis

Summary The highly coiled testicular artery within the bovine spermatic cord has a constant luminal diameter but a continuously decreasing mural thickness. The pampini form plexus is composed of three interconnected venous networks differing in mesh sizes and calibres. The large veins of the first network display pouches and permanent constrictions, which may serve as throttle devices. The constitutents of the third network are venules or venous capillaries with diameters between 10 and 20 m; they favor a periarterial position or even occupy the media-adventitia border of the testicular artery. All plexus veins are devoid of valves. The existence of true arteriovenous anastomoses between smaller branches of the testicular artery and plexus veins was established by serial sections. The vascular morphology of the spermatic cord is discussed with special attention to a postulated venous-arterial steroid transfer in this region.Supported by the Deutsche Forschungsgemeinschaft and the Stiftung zur Förderung der wissenschaftlichen Forschung an der Universität Bern     

Renal vascular anatomy of the toad (Bufo marinus)

The renal vasculature of the toad, Bufo marinus, was studied mainly by means of scanning electron microscopy of vascular corrosion casts. All arterial branches terminated in a glomerulus. Each glomerulus was supplied by only one afferent arteriole. No shunts between afferent and efferent arterioles were observed. The glomerular channels appeared to be permanent capillaries. No evidence supporting the theory of freely shifting glomerular blood channels was found. Efferent arterioles radiated out towards the dorsal surface of the kidney where they connected with peritubular vessels. The renal portal veins produced an anastomosing plexus on the dorsal surface of the kidney, giving rise to the peritubular vessels. Peritubular vessels ran radially toward the ventral surface of the kidney, where they formed the roots of the renal veins. Attention is drawn to the possibility of hairpin countercurrent exchange between the capillary-like efferent arterioles and the peritubular vessels in the dorsal kidney.     

The vascularization of the neural stalk and the pars nervosa of the hypophysis in the toad,Bufo bufo (L.) (amphibia,anura)

The angioarchitecture of the neural stalk and the encephaloposthypophysial portal system of the hypophysis of the toad, Bufo bufo (L.), was studied using three different methods. The neural stalk is mainly supplied by branches of the arteria infundibularis superficialis which form a widemeshed vascular network. Dorsally this network continues into the plexus of the pars nervosa. The vascularization of the pars nervosa is made up of the encephalo-posthypophysial portal system. This portal system consists of a hypothalamic branch (=portion), a mesencephalic and a mesencephalicbulbar branch (=portion). The hypothalamic branch was found to drain the pars ventralis of the tuber cinereum as well as more dorsal regions of the diencephalon. The mesencephalic-bulbar trunk enters the hypothalamic branch. The resulting common stem of the encephalo-posthypophysial portal vein the curves around the retroinfundibular communicating artery, crosses its ventral side and runs caudally. The secondary capillary plexus of the pars nervosa is characterized by well defined capillary plexus of the pars nervosa is characterized by well defined capillary networks which are located at the periphery of the parenchyma of the pars nervosa, thus forming a rostral, dorsal and ventro-caudal net. The central region of the parenchyma of the pars nervosa is supplied only by main branches of the encephalo-postpophysial portal vein. The venous drainage of the pars nervosa is via the vena hypophysea transversa.     

Effects of selection and fate of substrates supplied to anaerobic bacteria involved in the corrosion of pipe-line steel

Summary The corrosion of AISI C1020 carbon steel in an anoxic, marine, sulphide-containing environment was examined as a function of bacterial physiology and consortial complexity. The carbon steel was exposed to three organism;Eubacterium limosum, Desulfovibrio sp. andDesulfobacter sp. which were provided with H₂/CO₂, butanol, glucose, and acetate as carbon and electron sources. A consortium of these bacteria utilizing hydrogen gave rise to relatively high corrosion rates (5.7×10^–4 mhos cm^–2) with respect to corrosion resulting from bacteria supplied with organic electron sources (0.6–1.6×10^–4 mhos cm^–2). Disproportionation of electrons between sulphate reduction and fermentation had a significant effect on the corrosion rate in the case ofDesulfovibrio. Surface examination using scanning electron microscopy coupled with electrochemical impedance spectroscopy supported the hypothesis that the corrosion rate was controlled by the relative intactness of a ferrous sulphide film in which the bacteria were embedded.     

Achieving Balanced Crystallization Kinetics of Donor and Acceptor by Sequential‐Blade Coated Double Bulk Heterojunction Organic Solar Cells

Sequential deposition has great potential to achieve high performance in organic solar cells due to the resulting well‐controlled vertical phase separation. In this work, double bulk heterojunction organic solar cells are fabricated by sequential‐blade cast in ambient conditions. Probed by the in situ grazing incidence X‐ray diffraction and in situ UV–vis absorption measurements, the seq‐blade system exhibits a different tendency from each of the binary films during the film formation process. Due to the extensive aggregation of FOIC, the binary PBDB‐T:FOIC film displays a strong and large phase separation, resulting in low current density (J_sc) and unsatisfactory power conversion efficiency. In the seq‐blade cast system, the bottom layer PBDB‐T:IT‐M produces many crystal nuclei for the top layer PBDB‐T:FOIC, so the PBDB‐T molecules are able to crystallize easily and quickly. Balanced crystallization kinetics between polymer and small molecule and an ideal percolation network in the film are observed. In addition, the balanced crystallization kinetics are favorable toward realizing lower recombination loss through charge transport processes.     

Fecundity,nymphal development and longevity of field‐collected tropical bedbugs,Cimex hemipterus

This study examined the fecundity, oviposition, nymphal development and longevity of field‐collected samples of the tropical bedbug, Cimex hemipterus (Fabricius) (Hemiptera: Cimicidae). Under environmental conditions of 26±2°C, 70 ± 5% relative humidity and a 12‐h photoperiod, with bloodmeals provided by a human host, six strains of tropical bedbug had a fecundity of up to 50 eggs per lifetime, over 11–14 oviposition cycles. Increased feeding frequency improved fecundity. After feeding and mating, adult females normally took 2–3 days to produce a first batch of eggs. The oviposition period lasted 2–7 days before cessation of the oviposition cycle. The egg incubation period usually lasted 5–7 days before the emergence of first instars. The nymphs underwent five stadia (the first four of which each took 3–4 days, whereas the last took 4–5 days) before becoming adults at a sex ratio of 1 : 1. More than five bloodmeals were required by the nymphs to ensure a successful moult. Unmated adults lived significantly longer than mated adults (P < 0.05). Unmated females lived up to almost 7 months, but the longevity of mated males and females did not differ significantly (P > 0.05).     

Anatomy of the crocodilian spinal vein

The crocodilian spinal vein is remarkably robust yet historically overlooked. Using corrosion casting, we describe the anatomy of this vessel and its connections with the caval and hepatic venous systems in representatives from four crocodilian genera. The spinal vein arises from an enlarged occipital sinus over the medulla and extends the entire length of the vertebral column. Unlike in squamate reptiles, the spinal vein is single (nonplexiform), voluminous, and situated dorsal to the spinal cord, and plexi lateral to the cord span between emerging intercostal veins. The connections with the other venous systems are otherwise similar to those in other tetrapods. The overall anatomy of this vessel and its abundant connections with the other venous systems indicate it likely plays a primary role in returning blood to the heart from all parts of the body. Preliminary studies of function suggest that this vessel could also play an adaptive role during basking and diving.     

Endocranial cast and morphology of the olfactory bulb of<Emphasis Type="Italic"> Amphipithecus mogaungensis</Emphasis> (latest middle Eocene of Myanmar)

A detailed endocranial cast of the olfactory bulb of Amphipithecus mogaungensis, a latest middle Eocene primate from the Pondaung Formation (Myanmar), was studied in comparison with some Paleogene primates, the olfactory bulb of which has been reported. The olfactory bulb of Amphipithecus is located just anterior to the postorbital constriction, that is, within the interorbital septum. It is relatively large and pedunculate, not overlapped by the frontal lobe, and consists of two parallell aligned bodies. The relative volume of the olfactory bulb shows the same pattern as in adapiforms, but the location and bilobed form are more similar to those of omomyoids than of adapiforms. Electronic Publication     

氟对镍钛拉簧的腐蚀性研究

目的:研究模拟应用氟化物防龋的口腔环境下,不同浓度氟化物对镍钛拉簧的应力衰减的影响。方法:选取两种国内常用品牌0.010 inch镍钛拉簧各40根,随机将每种拉簧平均分入四个浓度组(0.05%、0.10%、0.15%和对照组),将相同浓度组的不同品牌弹簧分别固定于间距为20 mm的四个支架的两端。将四个支架分别放入37℃人工唾液中水浴。将实验组按浓度分组放入不同浓度氟化人工唾液(0.05%、0.10%、0.15%)中处理5 min,每天三次。分别于实验前、实验后1周、2周、3周、4周用拉伸机测量每根弹簧拉伸至20 mm时的应力。对实验结果使用重复测量的方差分析。结果:时间因素对两种镍钛拉簧拉伸应力的衰减的影响有统计学意义,氟化物浓度有辅助效应,二者有交互作用。氟化物作用下不同品牌镍钛拉簧的应力腐蚀变化不同。(P0.05)。结论:1.氟化物的存在可以增加镍钛拉簧的应力衰减。2.在正畸治疗的临床工作中在使用氟化物时应考虑增加镍钛拉簧的更换频率。