3D Dune Skeleton Model as a Coupled Dynamical System of 2D Cross-Sections

To analyze theoretically the stability of the shape and the migration process of transverse dunes and barchans, we propose a {\it skeleton model} of 3D dunes described with coupled dynamics of 2D cross-sections. First, 2D cross-sections of a 3D dune parallel to the wind direction are extracted as elements of a skeleton of the 3D dune, hence, the dynamics of each and interaction between them is considered. This model simply describes the essential dynamics of 3D dunes as a system of coupled ordinary differential equations. Using the model we study the stability of the shape of 3D transversal dunes and their deformation to barchans depending on the amount of available sand in the dune field, sand flow in parallel and perpendicular to wind direction.Comment: 6 pages, 6 figures, lette

Comment on the Generation Number in Orbifold Compactifications

There has been some confusion concerning the number of $(1,1)$-forms in orbifold compactifications of the heterotic string in numerous publications. In this note we point out the relevance of the underlying torus lattice on this number. We answer the question when different lattices mimic the same physics and when this is not the case. As a byproduct we classify all symmetric $Z_N$-orbifolds with $(2,2)$ world sheet supersymmetry obtaining also some new ones.Comment: 28 pages, 9 figures not included, available in postscript at reques

Measurement of the electron transmission rate of the gating foil for the TPC of the ILC experiment

We have developed a gating foil for the time projection chamber envisaged as a central tracker for the international linear collider experiment. It has a structure similar to the Gas Electron Multiplier (GEM) with a higher optical aperture ratio and functions as an ion gate without gas amplification. The transmission rate for electrons was measured in a counting mode for a wide range of the voltages applied across the foil using an $^{55}$Fe source and a laser in the absence of a magnetic field. The blocking power of the foil against positive ions was estimated from the electron transmissions.Comment: 25 pages containing 14 figures and 1 tabl

Ectopic A-lattice seams destabilize microtubules

Natural microtubules typically include one A-lattice seam within an otherwise helically symmetric B-lattice tube. It is currently unclear how A-lattice seams influence microtubule dynamic instability. Here we find that including extra A-lattice seams in GMPCPP microtubules, structural analogues of the GTP caps of dynamic microtubules, destabilizes them, enhancing their median shrinkage rate by >20-fold. Dynamic microtubules nucleated by seeds containing extra A-lattice seams have growth rates similar to microtubules nucleated by B-lattice seeds, yet have increased catastrophe frequencies at both ends. Furthermore, binding B-lattice GDP microtubules to a rigor kinesin surface stabilizes them against shrinkage, whereas microtubules with extra A-lattice seams are stabilized only slightly. Our data suggest that introducing extra A-lattice seams into dynamic microtubules destabilizes them by destabilizing their GTP caps. On this basis, we propose that the single A-lattice seam of natural B-lattice MTs may act as a trigger point, and potentially a regulation point, for catastrophe

Discrete R-symmetries and Anomaly Universality in Heterotic Orbifolds

We study discrete R-symmetries, which appear in 4D low energy effective field theory derived from hetetoric orbifold models. We derive the R-symmetries directly from geometrical symmetries of orbifolds. In particular, we obtain the corresponding R-charges by requiring that the couplings be invariant under these symmetries. This allows for a more general treatment than the explicit computations of correlation functions made previously by the authors, including models with discrete Wilson lines, and orbifold symmetries beyond plane-by-plane rotational invariance. Surprisingly, for the cases covered by earlier explicit computations, the R-charges differ from the previous result. We study the anomalies associated with these R-symmetries, and comment on the results.Comment: 21 pages, 2 figures. Minor changes, typos corrected. Matches JHEP published versio

Searching singlet extensions of the supersymmetric standard model in Z6−II Z_{6-II} orbifold compactification of heterotic string

We search for supersymmetric standard model realizations with extra singlets and extra $U(1)$ using the heterotic string compactification on the $Z_{6-II}$ orbifold with two Wilson lines. We analyze the vacuum restabilization mechanism for three representative Pati-Salam string models obtained in the literature and present detailed results for the effective superpotential compatible with the string selection rules. An automated selection of semi-realistic vacua along flat directions in the non-Abelian singlet modes field space is performed by requiring the presence of massless pairs of electroweak Higgs bosons having trilinear superpotential couplings with massless singlet modes and the decoupling of color triplet exotic modes needed to suppress $B$ and $L$ number violating processes.Comment: revtex4 format, 21 pages, 7 tables, shortened version added reference

A case of serious laryngeal edema unpredictably detected during laryngoscopy for orotracheal intubation following induction of anesthesia

We report a case of unpredictable and serious laryngeal edema probably caused by preoperative esophagogastroduodenoscopy (EGD). A 54-year-old man with type 2 diabetes mellitus was scheduled to undergo coronary artery bypass grafting (CABG). Two days before surgery, EGD was performed to explore the cause of occult bleeding, resulting in a slightly sore throat and an increased white blood cell count (18,300/μl). Without premedication, general anesthesia was uneventfully induced with intravenous midazolam (10 mg) and fentanyl (50 μg), followed by inhalation of sevoflurane (3%) and intravenous rocuronium (50 mg). Thereafter, manual ventilation was easily performed with a bag and mask. However, on laryngoscopy for orotracheal intubation, serious swelling with rubor and light pus in the epiglottis extending to the arytenoid cartilage was detected, leading to the cancellation of surgery. Immediately following intravenous drip of hydrocortisone (300 mg) and bolus of sugammadex (200 mg), the patient recovered smoothly from anesthesia without complications such as dyspnea, but his sore throat persisted. He was diagnosed with acute epiglottitis. Treatment consisted of intravenous cefazolin (2 g/day) and hydrocortisone (300 mg/day tapered to 100 mg/day) for 9 consecutive days. Consequently, the patient recovered gradually from the inflammation and underwent CABG as scheduled 28 days later. Anesthesiologists should be aware that EGD performed just before anesthesia could unpredictably cause acute epiglottitis, especially in immunocompromised patients, such as those with diabetes

Total Synthesis of Decahydroquinoline Poison Frog Alkaloids ent-\u3ci\u3ecis\u3c/i\u3e-195A and \u3ci\u3ecis\u3c/i\u3e-211A

The total synthesis of two decahydroquinoline poison frog alkaloids ent-cis-195A and cis-211A were achieved in 16 steps (38% overall yield) and 19 steps (31% overall yield), respectively, starting from known compound 1. Both alkaloids were synthesized from the common key intermediate 11 in a divergent fashion, and the absolute stereochemistry of natural cis-211A was determined to be 2R, 4aR, 5R, 6S, and 8aS. Interestingly, the absolute configuration of the parent decahydroquinoline nuclei of cis-211A was the mirror image of that of cis-195A, although both alkaloids were isolated from the same poison frog species, Oophaga (Dendrobates) pumilio, from Panama