60 research outputs found
Ascarophis arctica Polyanskiy 1952
No full text<i>Ascarophis arctica</i> Polyanskiy, 1952 Figs. 12–14 <p> <b>Description.</b> Small, whitish nematodes. Cuticle thick, with fine transverse striations (Figs. 13B,C, 14D). Cephalic end rounded, with two conspicuous conical pseudolabial terminal protrusions (Figs.12A–E, 13A–C). Oral aperture oval, with lateral extensions. Four submedian labia and 4 submedian flap-like sublabia well developed. Lateral pseudolabia well developed, each provided with conspicuous terminal protrusion; in apical view, flat inner parts of pseudolabia partly cover mouth and are distinctly dorsoventrally expanded, forming 2 (1 dorsolateral and 1 ventrolateral) extensions on each; inner margins of both pseudolabia dorsoventrally straight, parallel to each other (Figs. 12F, 13A–D). Four elongate submedian cephalic papillae and pair of lateral amphids present (Figs. 12F, 13A–C). Vestibule (stoma) long, cylindrical, with small funnel-shaped prostom in lateral view (Fig. 12A–E). Glandular oesophagus in female 6–8 times longer than muscular; both parts of oesophagus distinctly separated from each other (Fig. 12A). Nerve ring encircles muscular oesophagus approximately at border of its first and second thirds; excretory pore located somewhat posterior to level of nerve ring; deirids very small, bifurcate, situated somewhat posterior to end of vestibule (Figs. 12A–C,E,G, 13F).</p> <p> <b>Male</b> (1 specimen with missing anterior part of body). Length of body fragment 3.56, maximum width 51. Incomplete glandular oesophagus 653 long, maximum width 45. Posterior end of body ventrally curved, provided with narrow caudal alae. Preanal papillae: 4 pairs of subventral pedunculate papillae present, of which first and second and third and fourth are shifted in relation to each other, alternating along margins of tail (Figs. 12I,H, 14A–D). Postanal papillae: 6 pairs present, including 5 pairs of pedunculate subventral papillae and 1 pair of minute ventral sessile papillae located slightly posterior to level of last pair of subventrals (Figs. 12I, 14B). Small median ventral caudal protuberance present at tail tip (Fig. 14D). Ventral cuticular ridges (area rugosa) anterior to cloaca weakly developed, consisting of about 7 longitudinal tessellated ornamentations (Fig. 14C,D). Large (left) spicule 681 long, with pointed distal tip; its shaft 279 long, forming 41% of overall length of spicule (Figs. 12I,H, 13G). Small (right) spicule boat-shaped, 81 long, with rounded distal end (Fig. 12I,H). Length ratio of spicules 1: 8.4. Tail conical, 84 long, with rounded tip (Fig. 14A,B,D).</p> <p> <b>Female</b> (6 gravid specimens with mature eggs). Length of body 8.3–10.9 mm, maximum width 81–105. Height of cephalic protrusions 3. Vestibule including prostom 90–105 long; prostom 12 long, 12–15 wide. Length of muscular oesophagus 219–264, maximum width 18–27; length of glandular oesophagus 1.22–1.89 mm, maximum width 42–57; length ratio of muscular and glandular parts of oesophagus 1: 5.6–7.6. Length of entire oesophagus and vestibule represents 17–22% of total body length. Nerve ring, excretory pore and deirids 162–198, 207–300 and 129–135, respectively, from anterior extremity. Vulva somewhat postequatorial, situated 5.07–6.09 mm from anterior end of body, at 56–69% of body length; vulval lips not elevated. Vagina directed posteriorly from vulva. Amphidelphic. Uterus filled with numerous eggs. Mature eggs (containing larvae) oval, thick-walled, size 48–54 × 24–27; thickness of egg wall 4–5. Each pole of egg mostly with small knob provided with 2–5 thread-like filaments; knob on 1 pole somewhat larger than that on opposite pole, usually bearing 0–3 short, fine filaments and 2 thicker and longer filaments; filaments growing up from smaller knob relatively short and fine, 2–3 in number (Figs. 12L, 14E,F); exceptionally knob and filaments present only on 1 pole of larvated egg (Fig. 14G). Tail conical, short, 39–57 long, with 2 lateral papilla-like phasmids near its tip, and a distinct small terminal knob-like projection (Figs. 12K, 13E).</p> <p> Host: Three-spined stickleback, <i>Gasterosteus aculeatus</i> Linnaeus (Gasterosteidae, Gasterosteiformes).</p> <p>Site of infection: Stomach.</p> <p>Locality: Nishittapu River, Tomakomai, Hokkaido, Japan (collected 16 June 1996 and 19 June 2009).</p> <p>Total prevalence and intensity: 25% (3 fish infected/12 fish examined); 1–6 (mean 3) nematodes per fish. 1996: 1 fish infected, fish size not measured/1 fish examined; 3 nematodes. 2009: 18% (2 fish infected, 7.1 and 8.2 cm TL/11 fish examined, 7.9–9.1 cm TL); 1 and 6 nematodes.</p> <p>Deposition of voucher specimens: IPCAS N-1153.</p> <p> <b>Remarks.</b> The general morphology of the present nematodes from <i>G</i>. <i>aculeatus</i> indicates that they belong to the nominotypical subgenus <i>Ascarophis</i> van Beneden, 1870 (see Moravec and Justine 2009) of the cystidicolid genus <i>Ascarophis</i> van Beneden, 1870, as defined by Ko (1986). At present, 41 species of this genus are considered to be valid (Moravec et al. 2018).</p> <p> Only the following seven species of the genus <i>Ascarophis</i> have filamented eggs and a large (left) spicule length similar to that of the species under study (681 µm): <i>A</i>. <i>arctica</i> (left spicule 500–980 µm long), <i>Ascarophis draconi</i> Muñoz et George-Nascimento, 2007 (482–640 µm), <i>Ascarophis litoralica</i> Zhukov, 1960 (590–670 µm), <i>Ascarophis marina</i> (Szidat, 1961) (405–600 µm), <i>Ascarophis morrhuae</i> van Beneden, 1870 (500–790 µm), <i>Ascarophis maulensis</i> (Muñoz, González et George-Nascimento, 2004) (550–690 µm) and <i>Ascarophis richeri</i> Moravec et Justine, 2007 (663–729 µm) (Ferrer et al. 2005, Muñoz et al. 2004, Moravec and Justine 2007, Muñoz and George-Nascimento 2007). Of these, however, <i>A</i>. <i>marina</i>, <i>A</i>. <i>maulensis</i> and <i>A</i>. <i>richeri</i> have a different structure of the mouth and they belong to the subgenus <i>Similascarophis</i> Muñoz, González et George-Nascimento, 2004 (see Moravec and Justine 2007). The remaining four species are representatives of the subgenus <i>Ascarophis</i>, as are the present specimens from <i>G</i>. <i>aculeatus</i>.</p> <p> However, <i>A</i>. <i>draconi</i> has much longer males and females (males 9.9–13.3 mm, females 20.9–28.6 mm) and the eggs have two filaments on each pole; <i>A</i>. <i>litoralica</i> has also eggs with only two filaments on each pole, whereas its body measurements are similar to those of the present nematodes from Japan. Both <i>A</i>. <i>draconi</i> and <i>A</i>. <i>litoralica</i> were described from the Pacific Ocean (off Chile and in the South-Kurile shallow waters, respectively) (Zhukov 1960, Muñoz and George-Nasciento 2007); the latter species has not yet been studied by SEM.</p> <p> Two other species, <i>A</i>. <i>arctica</i> and <i>A</i>. <i>morrhuae</i>, were reported from different marine fishes (mostly Gadiformes and Scorpaeniformes) in the Atlantic and Arctic Oceans, being separated from each other mainly by the number and arrangement of egg filaments (two filaments only on one egg pole in <i>A</i>. <i>morrhuae</i> and several filaments on both egg poles in <i>A</i>. <i>arctica</i>) (Polyanskiy 1952, Appy 1981, Ko 1986, Fagerholm and Berland 1988). However, as confirmed in this paper, the number and character of egg filaments may be rather variable within the same species of <i>Ascarophis</i> and, therefore, should not be overestimated as a taxonomic feature.</p> <p> The original description of <i>A</i>. <i>morrhuae</i> by van Beneden (1870) was poor and, as pointed out by Zhukov (1960), apparently more congeneric species were included under this name from different hosts by subsequent authors. Therefore, a detailed redescription of this type species of <i>Ascarophis</i>, based on specimens newly collected from the type host and the type locality (off the coast of Belgium) is needed.</p> <p> The general morphology of the present nematodes from <i>G</i>. <i>aculeatus</i> shows that these can be assigned, according to present criteria, to <i>A</i>. <i>arctica</i>, even though, as compared with the descriptions of <i>A</i>. <i>arctica</i> from other fish hosts (Polyanskiy 1952, Appy 1981, Fagerholm and Berland 1988), the filaments on both poles of larvated eggs of these nematodes are less numerous (2–5 <i>vs</i> up to18 on each pole according to Fagerholm and Berland 1988) and the knob from which filaments are growing is distictly smaller on one egg pole as compared to that on the opposite pole, and ventral precloacal ridges in the male are poorly developed (<i>vs</i> well developed). In addition to the presence of several filaments on each pole in the majority of larvated eggs, these nematodes possess flap-like sublabia (Figs.12F, 13A–D), typical of <i>A</i>. <i>arctica</i>, as visible on SEM micrographs of Appy (1981) and Fagerholm and Berland (1988). Specimens of <i>A</i>. <i>morrhuae</i> from its type host (<i>Gadus morhua</i> Linnaeus) have not yet been studied by SEM, but those from <i>Trisopterus capellanus</i> (Lacépède) had distinctly bi-lobed sublabia (see fig. 75 of Ko 1986), although specimens from <i>Agonus cataphractus</i> (Linnaeus), also considered by Ko (1986) to be <i>A</i>. <i>morrhuae</i>, possessed flap-like sublabia.</p> <p> <i>Ascarophis arctica</i> was originally described from the stomach of the eelpout <i>Zoarces viviparus</i> (Linnaeus) (Zoarcidae, Perciformes) in the Barents Sea (Polyanskiy 1952) and subsequently it was also reported from different marine, mostly gadiform and scorpaeniform fishes in the North Atlantic region (Canada, Europe) (Appy 1981, Fagerholm and Berland 1988). The only record of <i>A</i>. <i>arctica</i> from <i>G</i>. <i>aculeatus</i> is that of Levsen (1992), who, without giving any morphological data, listed this nematode as a parasite of this fish species in western Norway (Bergen area). Therefore, the present finding of this parasite in Japan represents the first record of <i>A</i>. <i>arctica</i> in the region of the Pacific Ocean. Its host, <i>G</i>. <i>aculeatus</i>, is distributed in circumarctic and temperate regions of Northern Hemisphere (Froese and Pauly 2018). Hanek and Threlfall (1970) reported a different species of <i>Ascarophis</i>, <i>A</i>. <i>morrhuae</i>, as a common parasite of <i>G</i>. <i>aculeatus</i> in Newfoundland and Labrador, Canada, but no morphological data were provided.</p> <p> The Nishittapu River population of <i>G. aculeatus</i> is composed of both anadromous and fluvial indviduals (Higuchi and Goto 1994, 1996; they reported this river erroneously as the Nishikitappu River): the former individuals migrate to the sea for feeding and return to the river for spawning. The infected fish found in this study are considered to have become parasitised by <i>A</i>. <i>arctica</i> at sea.</p> <p> According to Nagasawa (2016), to date the only record of a species of <i>Ascarophis</i> from Japanese inland fishes is that of Margolis (1957), who reported <i>Ascarophis</i> sp. from the pink salmon <i>Oncorhynchus gorbuscha</i> (Walbaum). Several years ago, we examined two damaged males of <i>Ascarophis</i> from the stomach of the same host species (<i>O</i>. <i>gorbuscha</i>) in the Shikiu River, Hokkaido (collected 14 August 1981), provided by Dr. Shigehiko Urawa (Hokkaido National Fisheries Research Institute, Sapporo, unpublished). Since their left spicule was much shorter (264 and 288 µm) than that of <i>A</i>. <i>arctica</i>, they evidently belonged to a different species. However, having no conspecific females, their identification to species was impossible. Zhukov (1960) reported seven <i>Ascarophis</i> spp. from marine fishes (not Salmonidae) in the Sea of Japan and South-Kurile shallow waters, of which <i>Ascarophis japonicus</i> Zhukov, 1960 and <i>Ascarophis pacificus</i> Zhukov, 1960 have the left spicule length similar to that of <i>Ascarophis</i> sp. parasitising <i>O</i>. <i>gorbuscha</i>. More attention should be paid to <i>Ascarophis</i> sp. from salmon in Japan.</p>Published as part of <i>Moravec, František & Nagasawa, and Kazuya, 2018, Rhabdochona angusticaudata sp. n. (Nematoda: Rhabdochonidae) from the Japanese eel Anguilla japonica, and new records of some other nematodes from inland fishes in Japan, pp. 1-22 in Folia Parasitologica (016) (016) 65</i> on pages 15-19, DOI: 10.14411/fp.2018.016, <a href="http://zenodo.org/record/8143564">http://zenodo.org/record/8143564</a>
Lasers as particle accelerators in medicine: from laser‐driven protons to imaging with Thomson sources
No full textWe report our recent progress using a high‐power, picosecond CO2 laser for Thomson scattering and ion acceleration experiments. These experiments capitalize on certain advantages of long‐wavelength CO2 lasers, such as their high number of photons per energy unit and beneficial wavelength‐ scaling of the electrons’ ponderomotive energy and critical plasma frequency. High X‐ray fluxes produced in the interactions of the counter‐propagating laser‐ and electron‐beams for obtaining single‐shot, high‐contrast images of biological objects. The laser, focused on a hydrogen jet, generated a monoenergetic proton beam via the radiation‐pressure mechanism. The energy of protons produced by this method scales linearly with the laser’s intensity. We present a plan for scaling the process into the range of 100‐MeV proton energy via upgrading the CO2 laser. This development will enable an advance to the laser‐driven proton cancer therapy
Likelihood-free hypothesis testing
No full textConsider the problem of binary hypothesis testing. Given coming from
either or , to decide between
the two with small probability of error it is sufficient, and in many cases
necessary, to have , where measures the
separation between and in total variation
(). Achieving this, however, requires complete knowledge of the
distributions and can be done, for example, using the Neyman-Pearson test. In
this paper we consider a variation of the problem which we call likelihood-free
hypothesis testing, where access to and is given
through i.i.d. observations from each. In the case when and
are assumed to belong to a non-parametric family, we demonstrate
the existence of a fundamental trade-off between and given by nm\asymp
n_\sf{GoF}^2(\epsilon), where n_\sf{GoF}(\epsilon) is the minimax sample
complexity of testing between the hypotheses vs
. We show this for three
families of distributions, in addition to the family of all discrete
distributions for which we obtain a more complicated trade-off exhibiting an
additional phase-transition. Our results demonstrate the possibility of testing
without fully estimating and , provided .Comment: 58 pages, 1 figur
Kernel-Based Tests for Likelihood-Free Hypothesis Testing
No full textGiven observations from two balanced classes, consider the task of
labeling an additional inputs that are known to all belong to \emph{one} of
the two classes. Special cases of this problem are well-known: with complete
knowledge of class distributions () the problem is solved optimally
by the likelihood-ratio test; when it corresponds to binary
classification; and when it is equivalent to two-sample testing.
The intermediate settings occur in the field of likelihood-free inference,
where labeled samples are obtained by running forward simulations and the
unlabeled sample is collected experimentally. In recent work it was discovered
that there is a fundamental trade-off between and : increasing the data
sample reduces the amount of training/simulation data needed. In this
work we (a) introduce a generalization where unlabeled samples come from a
mixture of the two classes -- a case often encountered in practice; (b) study
the minimax sample complexity for non-parametric classes of densities under
\textit{maximum mean discrepancy} (MMD) separation; and (c) investigate the
empirical performance of kernels parameterized by neural networks on two tasks:
detection of the Higgs boson and detection of planted DDPM generated images
amidst CIFAR-10 images. For both problems we confirm the existence of the
theoretically predicted asymmetric vs trade-off.Comment: 36 pages, 6 figure
A Tight Upper Bound for the Third-Order Asymptotics for Most Discrete Memoryless Channels
No full textThis paper shows that the logarithm of the ε-error capacity (average error probability) for n uses of a discrete memoryless channel (DMC) is upper bounded by the normal approximation plus a third-order term that does not exceed 1/2log n +O(1) if the ε-dispersion of the channel is positive. This matches a lower bound by Y. Polyanskiy (2010) for DMCs with positive reverse dispersion. If the ε-dispersion vanishes, the logarithm of the ε-dispersion capacity is upper bounded by n times the capacity plus a constant term except for a small class of DMCs and ε≥1/2. © 1963-2012 IEEE
Zero-error communication over adder MAC
No full textThesis: M. Eng., Massachusetts Institute of Technology, Department of Electrical Engineering and Computer Science, 2018.This electronic version was submitted by the student author. The certified thesis is available in the Institute Archives and Special Collections.Cataloged from student-submitted PDF version of thesis.Includes bibliographical references (pages 53-54).Adder MAC is a simple noiseless multiple-access channel (MAC), where if users send messages X₁, . . . ,X[subscript h] [epsilon] {0, 1}[superscript n], then the receiver receives Y = X₁ + · · · + X[subscript h] with addition over Z. Communication over the noiseless adder MAC has been studied for more than fifty years. There are two models of particular interest: uniquely decodable code tuples, and B[subscript h]-codes. In spite of the similarities between these two models, lower bounds and upper bounds of the optimal sum rate of uniquely decodable code tuple asymptotically match as number of users goes to infinity, while there is a gap of factor two between lower bounds and upper bounds of the optimal rate of B[subscript h]-codes. The best currently known B[subscript h]-codes for h >/- 3 are constructed using random coding. In this thesis, we study variants of the random coding method and related problems, in hope of achieving B[subscript h]-codes with better rate. Our contribution include the following. 1. We determine the rate achieved by changing the underlying distribution used in random coding. 2. We determine the rate of a list-decoding version of B[subscript h]-codes achieved by the random coding method. 3. We study several related problems about Rényi entropy.by Yuzhou Gu.M. Eng
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