Determination of the resonant harmonics of the error field from dynamic magnetic measurements in a tokamak

The possibility is discussed of determining the amplitude and phase of a static resonant error field in a tokamak by means of dynamic magnetic measurements. The method proposed assumes measuring the plasma response to a varying external helical magnetic field with a small (a few gauss) amplitude. The case is considered in which the plasma is probed by square pulses with a duration much longer than the time of the transition process. The plasma response is assumed to be linear, with a proportionality coefficient being dependent on the plasma state. The analysis is carried out in a standard cylindrical approximation. The model is based on Maxwell’s equations and Ohm’s law and is thus capable of accounting for the interaction of large-scale modes with the conducting wall of the vacuum chamber. The method can be applied to existing tokamaks.     

Site-specific DNA splicing: a general procedure for the creation of a restriction site at a predetermined position in a DNA sequence

A method is described for creating any of a wide array of restriction sites at a predetermined position in a known DNA sequence. The method utilizes the exonuclease activity of BAL 31 and a specially designed bifunctional oligodeoxynucleotide linker. The desired restriction site is generated when the linker is ligated to those BAL 31-digested DNA fragments which end with the target sequence. The proper ligation product is then identified by a highly specific hybridization procedure. The method is versatile and specific and is especially useful in the isolation of functional elements of a gene.     

Characterization of acetylcholinesterase activity from Drosophila melanogaster

The acetylcholinesterase activity of the fruit fly, Drosophila melanogaster, was characterized biochemically. The activity is associated with a glycoprotein which is divided between a detergent-extractable membrane-bound fraction and a soluble fraction. The acetylcholinesterase activity is concentrated in the head of the insect. Through pharmacological methods, greater than 95% of the cholinesterase is judged to be true acetylcholinesterase, and not pseudocholinesterase. As expected for an acetylcholinesterase, the enzyme has a high affinity for acetylthiocholine and is inhibited by excess concentrations of acetylthiocholine. The soluble enzyme is found predominantly as a 7.8 S form; a smaller amount of an approximately 6 S form is also present, and a greater than or equal to 14 S form may exist. The detergent-solubilized acetylcholinesterase has a sedimentation coefficient of 7.5 S in the presence of detergent. The thermal inactivation rates for the soluble and the membrane bound enzymes are markedly different.     

The modelling of fibre reorientation in soft tissue

In this paper, a hyperelastic and thermodynamically consistent model for soft tissue is developed that is able to describe the change of the initial orientation of the collagen fibres. Full numerical implementation is considered as well. The collagen architecture is assumed to reorient driven by a specific thermodynamical force. The anisotropy is described by a strain energy function, which is decomposed into a part related to the matrix and a part related to the fibres. The initial fibre orientation is defined by a structural tensor, while the current orientation is described by a time-dependent structural tensor, which results from the initial one by a rotational transformation. The rotation tensor is obtained via an integration process of a rate tensor, which depends on an adequately defined thermodynamical force. The integration is achieved via an exponential map algorithm, where it is shown that the rotation is necessarily a two-parametric one. Efficiency of the proposed formulation is demonstrated using some numerical examples.     

Design of Strain-Sensing Devices in Microscale by Using Surface Plasmon Polaritons

We have presented a strain-sensing device in microscale by using surface plasmon polaritons and multimode interference effects. The device is numerically investigated by the finite-difference time-domain method. Optimum depths and length of the structure are designed for sensing a strain. The size of the designed structure is several micrometers and is about a thousandth compared with a fiber Bragg grating strain sensor. The sensitivity of the designed structure is 11.34 pm/μ?? that is about ten times larger than that of a fiber Bragg grating strain sensor. The temperature sensitivity of the designed structure is 34.43 pm/ ^°C. This temperature sensitivity is three times larger than that of a fiber Bragg grating strain sensor. Therefore, temperature compensation techniques are needed for the structure. The presented structure has a simple design such as a plasmonic waveguide with a trench structure. The simple structural design device has a capability of being used in micro- and nano-electromechanical systems.     

Length control of extended protein structures in bacteria and bacteriophages

The length of the tail of bacteriophages is controlled by a protein which acts as a molecular ruler. The needle of the injectisome, which is assembled by the polymerization of subunits that are exported through the nascent injectisome, is functionally related to the tail of bacteriophages. Interestingly, its length is controlled by a protein, which is itself exported and acts as a molecular ruler that is coupled to a substrate specificity switch. The bacterial flagellum is evolutionarily related to the injectisome. The length of the hook is also controlled by a secreted protein. This protein acts as a substrate specificity switch and, possibly, also as a ruler.     

Substrate specificity of nuclease TT1 from Thermus thermophilus HB8

The substrate and the action mechanism of a nuclease named nuclease TT1, from the culture broth of an extreme thermophile, Thermus thermophilus HB8, were investigated. The enzyme is nonspecific for the sugar moiety and cleaves both single- and double-stranded DNAs, rRNA, tRNA and oligonucleotides irrespective of chain length to produce 5'-mononucleotides exonucleolitically. The action mechanism is processive and the enzyme shows no porality of degradation. The minimal unit as a substrate is a 5'-dinucleotide. The rate of hydrolysis is independent of a terminal phosphate group. The substrate lacking a 5'-phosphoryl group is degraded to leave the 5'-terminus and the penultimate nucleotide (NpN) as a core. The substrate possessing a 3'-phosphoryl group is degraded to leave the mononucleoside 5',3'-diphosphates (pNp). However, NpN and pNp are gradually degraded by a large dose of the enzyme to produce a 5'-mononucleotide. The enzyme is free from nonspecific phosphatase and phosphodiesterase activities. Application of this enzyme to determine the sequence of oligonucleotides is shown.     

长毛对虾精子发生的研究：Ⅰ.精子的形态结构

利用电子显微镜技术结合细胞化学染色方法,研究长毛对虾精子形态结构,结果显示:长毛对虾精子由圆球状球体部和钉子状棘突部组成;精子全长约7μm;棘突及与之相联的球体表面平滑无突起,而与棘突相对的球体底面有指状突起。透射和冷冻蚀刻电镜显示:长毛对虾精子棘突包括顶体锥和顶体帽两部分;顶体锥向外突出形成精子的棘突,顶体帽覆盖在球体部的胞质及核区上方。成熟精子胞质极度退化,仅靠顶体帽边缘可见1—2个线粒体。球体的中央区域为近球形,呈Feul-gen阳性反应,为精子的核区。其结构松散,电子密度低,属非浓缩型,内布许多絮状物质,外由许多长短不一的膜性结构不规则排列成不连续的核膜结构。研究结果认为:长毛对虾精子属不动无鞭毛精子类型,其棘突部并非鞭毛结构而是顶体的位置。     

Fine structure of the intersegmental membrane glands of the sixth abdominal sternum of female Nomia melanderi (Hymenoptera,Apoidea)

The fine structure of the intersegmental glands of the sixth abdominal sternum in 1-week old females of Nomia melanderi is presented. The plasma membrane of the secretory cell is unfolded in many places and is covered by a basement membrane. The microvillous surface is invaginated to form a rather long sinuous cavity. The endoplasm is almost entirely filled by secretory granules. Many secretory granules are located close to the inner surface of the invaginated plasma membrane. The invagination contains a porous ductule, apparently of cuticulin origin, that is connected directly with the inner layer of the transport duct of the duct-forming cell. This type of arrangement allows the direct flow of the secretory substance to the outside in a continuous way. The cylindrical duct-forming cell, besides having typical cell organelles, contains a cuticular transport duct. This duct is composed of a thin cuticulin layer surrounded by a rather thick epicuticular one. The results suggest that the secretory cell has two secretory cycles. The first occurs while the gland is differentiating (at the pupal stage) and is involved in secretion of the cuticulin that forms the porous ductule. The second cycle, which starts by the beginning of nesting, is involved in the secretion of a substance that is carried to the outside via the transport duct of the duct-forming cell.     

Copillaria hepatica: Fine structure of egg shell

The structure of the Capillaria hepatica egg shell was studied with the electron microscope and correlated with light microscope histochemical observations. The shell is composed of fibrous and nonfibrous components, both of which stain for protein. The fibrous component, the major portion of the shell, consists of submicroscopic fibers. The nonfibrous component is located in the outer region of the shell but is not always visible; when present it has a reticulated appearance in electron micrographs. The fibrous component is divided into outer and inner regions. The outer region is composed of radially arranged pillars which are connected at their outer surface by a beam-like network and are anchored at the base to a compact inner region. The inner region consists of a series of concentrically arranged lamellae above which is located a nonlaminated region where the pillar bases originate. At each polar end of the shell is a single opening plugged with a material which contains acid mucopolysaccharide. The fine structure of the body of the plug is unresolvable with the electron microscope; its outer surface is impregnated with electron dense particles. Externally the shell is covered by a 250 Å thick continuous membrane which is in close opposition to the surrounding host tissue.     

A differential scanning calorimeter for ice nucleation distribution studies--application to bacterial nucleators

A differential scanning calorimeter has been developed for the automatic detection and measurement of dropwise freezing within a sample of 100-200 water drops. A typical drop size of 1 microliter is employed. The sample is distributed on flat, square (4-cm) thermoelectric sensors and the temperature is scanned downward by conductive cooling to a liquid nitrogen bath. The rate of cooling, typically 1 degree C/min, is set by the choice of a heat conduction rod between the calorimeter and the liquid nitrogen bath. The voltages from the thermopiles along with a system temperature-measuring thermocouple are continuously monitored by digital voltmeters and recorded every half-second in a computer memory. A freezing event in a drop is detected by a characteristic voltage signal whose integral with time is proportional to the size of the drop and its heat of fusion. The half-life of a freezing event signal is 10 s for a 1-microliter drop. The integrated signal produced from multiple freezing events is shown to provide a direct measure of the number of drops frozen at a given temperature. A distribution curve and its smoothed derivative can be constructed directly from these measurements. The instrument, which is termed an "ice nucleometer," is illustrated in determining the ice nucleation distribution in a population of Escherichia coli harboring cloned ice nucleation genes.     

A Scanning Electron Microscope Study on the Internal Structure of the Peritreme of the Female Mite Varroa jacobsoni (Oudemans, 1904)

The peritreme of the adult female mite Varroa jacobsoni is located laterally above coxa III and is enclosed within a peritrematal shield which has a slit at the end. The peritrematal shield is cuticular in nature. The peritreme is lined with a thick inner membrane which has numerous tooth-like projections. The outer membrane of the peritreme is thin and smooth. In between these two membranes is a layer of columnar cells. The internal structure of the peritreme in relation to the female mite's ability to adjust to different atmospheric conditions is discussed.     

泥螺生殖系统的组织学

泥螺为雌雄同体。生殖系统包括交媾器和生殖器本部。交媾器包括刺激器、阴茎和摄护腺;生殖器本部主要包括两性腺、缠卵腺和蛋白腺。刺激器和阴茎都具有非常发达的肌肉组织,腔壁游离面具纤毛。阴茎腔壁为单层柱状细胞;摄护腺被膜为一层薄的肌纤维,里面具有许多分泌细胞;缠卵腺被膜为单层扁平上皮,下层为环肌,腺体组织由分泌小管构成。蛋白腺主要由皮质层和导管层组成,皮质层内充满了分泌细胞,导管层由许多分泌小管构成,管壁为柱状腺细胞。     

江苏泗洪下草湾中中新世脊椎动物群——6.鸟纲

本文记述了近年来在江苏泗洪下草湾组中补采到的6种鸟类,其中包括天岗琵鹭 Platalea tiangangensis sp. nov.和松林庄古石鸡 Palaeoalectoris songlinensis gen. et sp. nov.,前者系琵鹭属迄今最早的记录,后者为雉科鹑族目前已知最早的成员.     

Lectin affinity electrophoresis

Lectin affinity electrophoresis is a powerful technique to investigate the interaction between a lectin and its ligand. Affinity electrophoresis results from the reduced mobility of a charged species owing to its interaction with an immobile species. In this protocol, a two-dimensional lectin affinity electrophoresis experiment is described that affords separation of oligosaccharides. The first-dimension is composed of a weak, polyacrylamide, capillary tube gel containing a lectin. The example described involves a mixture of fluorescently labeled disaccharides. The mobility of only the lectin-binding disaccharide is reduced affording a separation in the first-dimension. The tube gel is then extruded and placed onto the second-dimension gradient polyacrylamide gel and subjected to electrophoresis. Mobility in the second-dimension is dependent on molecular size and visualization is by fluorescence under transillumination. This method is also applicable, with appropriate modifications, for the separation and analysis of glycopeptides and glycoproteins.     

四川盆地中侏罗世一肉食龙

七里峡宣汉龙(Xuanhanosaurus qilixiaensis gen. et sp. nov.)具有较发达的前肢和残存的第Ⅳ掌骨,是巨齿龙科中较原始的一种特征。据此推断其生存的时代为中侏罗世。     

Fine structure of the spermatozoa of Chiton marginatus (mollusca: Amphineura), with special reference to nucleus maturation

The spermatozoon of Chiton marginatus is a long uniflagellate cell displaying structural features of “modified sperm.” The nucleus presents a conical shape with a long apical cylindrical extension. The chromatin is homogeneously dense. Scattered inside the condensed nucleus, a few nuclear lacunae are visible. The acrosomal complex is lacking. Some mitochondria are located in a laterofrontal structure side by side with the nucleus. The typical midpiece is absent. The cytoplasm forms a thin layer around the nucleus and the mitochondria. The proximal centriole is in a basal nuclear indent. The distal centriole serves to form the axoneme tail with the usual microtubular pattern. During nuclear maturation, the early spermatid nucleus is spherical and contains fine granular chromatin patches. The nuclear envelope shows a deposit of dense material at the base of the nucleus, forming a semicircular invagination occupied by a flocculent mass. In middle spermatid stage, the chromatin gets organized in filaments, coiled as a hank, attached over the inner surface of the basal thickening of the nuclear envelope. The nucleus starts to elongate anteroposteriorly. At the pointed apical portion of the spermatid, a group of microtubules is observed seeming to impose external pressure to the nucleus giving rise to the long apical nuclear point. The mitochondria have a basal position. Late spermatids have an elongated conical nucleus. The chromatin filaments are further condensed, and lacunae appear inside the nucleus. Some mitochondria migrate to a lateral position.     

Circumauricular incision (water-drop shape) for mid- to lower face lift

The conventional method of mid- to lower face rhytidectomy that involves removing a strip of occipital scalp always creates a conspicuous transverse scar crossing the postauricular skin, which may leave a stair-step deformity at the occipital hairline. The author has designed a new face lift method using a circumauricular incision, shaped like a water droplet, that curves around the auricle. In this new method, the upper part of the "O" shape is modified to the tip of a water droplet. The dissection of the cheek and neck is performed as in the conventional method with light-retractor assistance. The temporal region above the deep temporal fascia is managed under endoscopic control. This dissection can extend to the forehead region lateral to the supraoptic nerve and around the lateral orbital rim to release the arcus marginalis. A mesentery of superficial temporal fascia is created cephalic to the zygomatic arch. The postauricular dissection is performed beneath the galea in the upper part and beneath the occipital scalp and neck skin in the lower area. The lifting vector is upward and backward for the anterior skin flap and upward for the posterior skin flap. The excess skin is trimmed around the ear. The wound at the upper pole of the incision is closed in a V-to-Y advancement fashion. The dog-ear is left above the normal hairline, and there is little or no hairy scalp to be removed. The skin pleating in the postauricular region will settle down spontaneously after several months. The dog-ear in the scalp will become smaller and flat as well. The scar around the ear is quite inconspicuous and well covered under the upper pole of the auricle. From the author's experience, the new "water drop" circumauricular incision is a good alternative for the mid- to lower face lift. It can also be used in conjunction with endoforehead lift for full-face rejuvenation.     

Information density, cellular immunity and transfer factor.

The problem of enzymatic and immunological specificity is considered as a question of recognition of 3-dimensional structure from the standpoint of information content and information density of a molecule. The implication of this model for chemical evolution is given. The idea that a double stranded RNA molecule cannot function as transfer factor (TF) is developed and a model for the formation of TF is suggested.     

An artificial membrane-cable: decay and delay of electrical potentials along a lipid bilayer with ion channels

A model membrane is described which exhibits the properties of a neurite with respect to passive propagation of electrical potentials. A groove in a glass plate is covered by a black lipid membrane of glycerol monooleate. Gramicidin is incorporated. The stationary and transient response of the assembly is tested by two experiments: (i) One end of the groove is clamped at a constant voltage. The voltage at the other end and the total electrical current are measured. (ii) A charge pulse is injected at one end of the groove. The time-dependent voltage at the other end is measured. The results with respect to the lateral decay and delay of voltage are in quantitative agreement with the stationary and transient solutions of Kelvin's equation for a homogeneous cable. If gramicidin is incorporated unevenly along the membrane, the lateral decay of voltage is found to be asymmetric with respect to both directions. The cable is a partial one-way transmission line.