Partial Twinning Research Articles

Partial twinning and the boundaries of a person

In special cases of partial twinning, two heads, each supporting a more-or-less normal human mental life, emerge from a single torso. It is often argued that there must be two people in such a case, even if there is only one biological organism. That would pose a problem for 'animalism', the view that people are organisms. The paper argues that it is very hard to say what sort of non-organisms the people in such cases would be. Reflection on partial twinning is no more comfortable for those who think we're not organisms than for those who think we are. We may have to accept that a single person could have two separate mental lives.

Anisotropic crystal orientations dependent mechanical properties and fracture mechanisms in zinc blende ZnTe nanowires.

The orientations of crystal growth significantly affect the operating characteristics of elastic and inelastic deformation in semiconductor nanowires (NWs). This work uses molecular dynamics simulation to extensively investigate the orientation-dependent mechanical properties and fracture mechanisms of zinc blende ZnTe NWs. Three different crystal orientations, including [100], [110], and [111], coupled with temperatures (100 to 600 K) on the fracture stress and elastic modulus, are thoroughly studied. In comparison to the [110] and [100] orientations, the [111]-oriented ZnTe NW exhibits a high fracture stress. The percentage decrease in fracture strength exhibits a pronounced variation with increasing temperature, with the highest magnitude observed in the [100] direction and the lowest magnitude observed in the [110] direction. The elastic modulus dropped by the largest percentage in the [111] direction as compared to the [100] direction. Most notably, the [110]-directed ZnTe NW deforms unusually as the strain rate increases, making it more sensitive to strain rate than other orientations. The strong strain rate sensitivity results from the unusual short-range and long-range order crystals appearing due to dislocation slipping and partial twinning. Moreover, the {111} plane is the principal cleavage plane for all orientations, creating a dislocation slipping mechanism at room temperature. The {100} plane becomes active and acts as another fundamental cleavage plane at increasing temperatures. This in-depth analysis paves the way for advancing efficient and reliable ZnTe NWs-based nanodevices and nanomechanical systems.

<p class="Body"><strong>Morphological abnormalities in ticks (Acari: Ixodidae) from the Republic of Korea</strong></p>

Tick-borne disease surveillance was conducted by tick drag among uncut grasses/herbaceous vegetation and mixed forest habitats from 2018–2020 at US Army Garrison Humphreys, Pyeongtaek, the Republic of Korea (ROK). While identifying ticks collected in the spring of 2020, teratological anomalies were observed in nymphs of Haemaphysalis longicornis (in one specimen, partial twinning of the posterior idiosoma, resulting in 2 anuses; in a second, asymmetry of the idiosoma) and Ixodes nipponensis (7 legs). These teratological observations in H. longicornis and I. nipponensis are reported for the first time in the ROK.

Türkiye’den Yeni Teratolojik Kene (Acari: Ixodidae) Örnekleri

During our survey on ticks parasitizing animals, two teratological tick specimens belonging to Ixodes frontalis (Panzer) and Rhipicephalus annulatus (Say) were collected from a bird and cattle, respectively. These samples exhibited unique morphological anomalies, including partial twinning of the posterior region of the idiosoma with two anal openings. To our knowledge, such teratological changes in I. frontalis and R. annulatus ticks have been reported for the first time.

Hot rolled and cold rolled medium manganese steel: Mechanical properties and microstructure

The current work aims at obtaining optimum amount of austenite after processing of a medium manganese steel in order to invoke partial twinning induced plasticity (TWIP) mechanism during deformation and to maximise elongation. Steel chemistry was optimised using thermodynamic calculations and the same was processed in different ways which includes continuous cooling from single phase austenitic region, quenching + austenite reverted transformation (ART) annealing and austenite reverted transformation (ART) annealing. DICTRA and Thermo-Calc simulation was done to understand the austenite to ferrite transformation kinetics during continuous cooling and the mode of equilibrium that is operative. The study suggests that quenching + austenite reverted transformation (ART) annealing is the ideal approach for processing this material in order to get the desired microstructure and properties. Thermo-Calc and Koistinen and Marburger's (KM) equation was coupled to estimate the fraction of austenite to be retained after isothermal holding at different intercritical temperatures and the optimum temperature found was used for annealing this steel. Microstructural characterization along with tensile test was done to ascertain the effect of processing route, initial microstructure on the mechanical properties. It was found that the morphology of austenite was greatly affected by the initial microstructure of the steel. Mechanical properties obtained after cold rolling (CR) and austenite reverted transformation (ART) annealing was found to be superior to that of hot rolling (HR) and austenite reverted transformation (ART) annealing. The difference in mechanical properties was correlated with the austenite morphology and the final microstructure.

First scientific record of two cases of partial twinning in the chick embryo, Gallus gallus domesticus

Bicephalia is one of the scarcest malformations reported in birds and needs to be fully investigated in chick embryos. Among 1500 fertilised eggs used to examine the primordial germ cells...

Abnormal Development of Haemaphysalis qinghaiensis (Acari: Ixodidae).

A single Haemaphysalis qinghaiensis specimen exhibiting abnormal morphology was collected from a tick laboratory colony. The tick had a heart-shaped body with partial twinning of the posterior region (with two anal orifices and two genital grooves). To the best of our knowledge, this is the first report of teratological changes in H. qinghaiensis. The abnormal morphological features are described herein.

Cyclic deformation and fatigue of extruded AZ31B magnesium alloy under different strain ratios

Cyclic deformation and fatigue behavior of extruded AZ31B magnesium (Mg) alloy were investigated under strain-controlled loading along the extrusion direction at different strain amplitudes with three strain ratios (Rε=0, −1, −∞). With a strain ratio of Rε=−∞, partial twinning-partial detwinning occurs at all strain amplitudes, leading to accumulation of deformation twins as the loading cycle is increased. With strain ratios being Rε=0 and −1, partial twinning–complete detwinning is the cyclic deformation mechanism when the strain amplitude is higher than 0.35%. At a strain amplitude lower than 0.35%, dominant cyclic deformation mechanism is dislocation slips irrespective of the strain ratio. Compared with the cases of Rε=0 and Rε=-1, stronger cyclic hardening is exhibited at all the investigated strain amplitudes for Rε=−∞. Fatigue fracture surfaces show regions with lamellar-like and dimple-like features. Lamellar-like feature existing in the crack initiation and stable propagation region are mainly due to twinning–detwinning during cyclic deformation. The dimple-like feature formed in the unstable crack propagation and final rupture region mainly arises from severe intra-granular plastic deformation by dislocation slips. At the same strain amplitude, the lamellar-like traces become more aggravated with a lower stain ratio. The strain–fatigue life curves exhibit a distinguishable kink at strain ratios Rε=−∞, −1 and 0. The fatigue life with Rε=−∞ shows the highest and that with Rε=0is the lowest at the same strain amplitude. The Smith–Watson–Topper (SWT) fatigue criteria can correlate well the fatigue experiments of AZ31B Mg alloy under different strain ratios.

Models of Dislocation Formation and Mechanical Twinning by Local Reversible Martensitic Transformations in FCC Nanocrystals

An atomic model is proposed which describes the formation of dislocations and deformation twins through a direct plus reverse martensitic transformation localized in two or several slip planes. The reasons and mechanisms for the formation of partial dislocations and mechanical twinning in nanocrystals under plastic deformation are discussed.

Gastric duplication cyst: An uncommon cause of pain abdomen in an adult

Duplication cysts are rare congenital developmental anamolies of the gastrointestinal tract, the etiology of which is not completely understood. Multiple theories have been proposed to explain their existence including partial twinning, in utero ischemic events, and abnormal endoderm and notochord separation. Complications including infection, intussusception, and perforation can occur. Rarely, these duplications cysts may undergo neoplastic changes. In this report, we present the case of a 40year-old male with a gastric duplication cyst who presented with vague postprandial dull-aching epigastric pain. Gastric duplication cyst was diagnosed with upper GI endoscopy and CT scan. The cyst was removed by simple excision and patient has remained symptom-free on follow up.

Crystal structure of a novel manganese-containing cupin (TM1459) from Thermotoga maritima at 1.65 A resolution.

Crystal structure of a novel manganese-containing cupin (TM1459) from Thermotoga maritima at 1.65 A resolution.

22] Detecting and overcoming crystal twinning

Twinning is fairly common in protein crystals. In its merohedral from, twinning is not apparent in the diffraction pattern, but the observed intensities do not represent individual crystallographic intensities. Since partial twinning (twin fraction less than 1/2) and perfect twinning (twin fraction of 1/2) can both be identified relatively easily by examining intensity statistics, the appropriate tests should be performed routinely when working in space groups that support merohedral twinning.

Abnormal development of Amblyomma variegatum (Acarina: Ixodidae).

Of 5,000 engorged Amblyomma variegatum larvae, 16 were observed with abnormal external features, centering on partial twinning of the posterior region of the body, with the presence of two anal pores and two genital grooves. According to the number of legs and spiracular plates, nymphs and adults were grouped into three types. Although there was only one midgut, it divided into a pair of hindguts, each of which opened into a separate rectal sac. In both sexes of adults, double reproductive organs were associated with two genital pores. All of the developmental stages fed well on rabbits. However, only one female oviposited and the eggs did not hatch.

A possible mechanism of partial twinning in a calf.

A two-headed calf had doubled heads and necks, externally normal forelimbs and thorax, incompletely doubled hearts and lungs, and a persistent sinus venosus, with abnormal pulmonary and systemic circulation. Study of the specimen indicated that partial twinning involved the development of the notochord as an anteriorly branched structure, with retention of the single condition posteriorly. It is proposed that anteroposterior compression of the embryonic disk could have induced the formation of double notochords. The way in which compression was produced is suggested.

Cranio-dirachischisis totalis in cephalothoracopagus twins.

A set of conjoined 13-day-old male hamster twins is described. The twins were joined at the head and thorax. The brain was exencephalic and the neural plate was completely open throughout its length. The notochord was duplicated throughout its entire length. Partial twinning of the neural plate as indicated by histologic reconstruction is suggested with fusion or non-separation of the neural plates in the medial alar wing area. There was complete separation of the neural plates together with duplication of the lower extremities and tails in the caudal region of this specimen.

Twinning of sand dollar embryos by means of dithiothreitol: The structural basis of blastomere interactions

In normally developing embryos of the sand dollar Dendraster excentricus the blastomeres are not tightly bound to each other at the end of cytokinesis. However, within 6 to 10 min the apposing cell surfaces appear flat against each other. Electron micrographs reveal that direct connection of the cell membranes exists. This process is called post-division adhesion. Dithiothreitol (DTT) destroys the ability of the blastomeres to initiate the post-division adhesion process and will also reverse this adhesion once it has formed. The result is that twin embryos develop if treatment occurs during or after the first cleavage. Extensive arrays of villi projecting from the cell surfaces in the region of the furrow are seen between blastomeres produced during exposure to DTT and in those fixed after cytokinesis before the post-division adhesion has occurred. Apparently, these villi pull the blastomeres together forming the tight contact in the normal condition. DTT destroys the ability of the villi to retract so the post-division adhesion does not occur and each blastomere develops as a twin although physically apposed to its sister. The twinning effect of DTT can be reversed to a degree by ferricyanide treatment. Single blastocoels develop in these embryos but evidence of partial twinning is seen in every embryo. The physiological isolation of each blastomere exposed to DTT is thought to involve the reduction of disulfide bonds in proteins. The destruction of the villi to function in blastomere adhesion may be caused by the destruction of microtubules or analogous structures necessary for their proper functioning.

The incorporation of slip dislocations in twins

The conditions for the incorporation of slip dislocations either propagating into a twin or engulfed by a growing twin are studied from the geometrical point of view. The resulting dislocation formed in a twin is independent of the mechanism of the incorporation. Under suitable conditions no stacking faults are formed at the twin boundary. The decomposition of twinning dislocations forming the noncoherent twin boundary is described using complementary partial twinning dislocations. The theory is formulated for both type I and II twins. Compound twins are also briefly treated in the discussion. Using the tensor notation all the formulae are given in the form valid for all crystal structures.

A natural population of anomalous branched tapeworms, Hymenolepis nana (Cestoda:Hymenolepididae), in a colony of DBA/1 mice.

DURING work on metabolism of the dwarf tapeworm of mice (Hymenolepis nana), a natural infection with this parasite was found in a local colony of DBA/1 mice (Curd's Caviary, Downey, California). Of 500 mice from this colony examined over a two-year period, 320 were infected with an average of 35 worms per mouse, varying from a single 12-in. worm to one or two thousand extremely small ones (demonstrating a ‘crowding effect’). Among more than 12,000 worms recovered, approximately 5 per cent showed one of the following malformations or growth disturbances : (1) Partial twinning (Fig. 1A) : forked posterior strobila ; (2) lateral branching (Fig. 1B) : new tissue outgrowth with varying degrees of differentiation ; (3) dedifferentiation (Fig. 1D) : groups of segments appearing as undifferentiated, vacuolated granular regions ; (4) segment reversal : reversal of normal antero-posterior sequence of proglottides (Fig. 1B) ; (5) combination : dedifferentiation plus branch outgrowth (Fig. 1C ; branch formation with segment reversal (Fig. 1B) ; multiple branching (Fig. 1E).

Cases of abnormal development in the argasid tick, Ornithodorus moubata

During the examination of over 8000 specimens of Ornithodorus moubata, two cases of partial twinning (one male, one female) of the posterior region were noticed, and also a case of suppression of the postanal region in a male. All the freaks were viable, and the partial twins were normally fertile.

Partial Twinning in a Stylet Cercaria

Partial Twinning in a Stylet Cercaria