Hypervelocity atomic oxygen source for the study of atom-surface interactions

Planned improvements in an electric discharge heated atomic oxygen beam source are described which will provide 6 to 7 kms(-1) beams of atomic oxygen with a flux of 10(16) cm(-2) s(-1) at 50 cm distance from the source aperture. A major advance will be the use of a zone of silence nozzle-skimmer arrangement which is necessitated by the need for high source flux and performance. It is anticipated that a Phase 2 program would provide for the fabrication of a two stage vacuum system which would be suitable for bolting on to a UHV (ultrahigh vacuum) surface study apparatus

Spherical alterations of handles: embedding the manifold plus construction

A key tool in our earlier work on ends of manifolds high-dimensional manifolds was an ability to embed cobordisms provided by the Quillen Plus Construction into those ends. Here we develop a `spherical modification' trick which provides a constructive approach to obtaining such embeddings. More importantly, this approach allows for more general embedding results. In this paper we develop generalizations of the plus construction and show how the corresponding cobordisms can be embedded in manifolds satisfying appropriate fundamental group properties. Results obtained here play an important role in our ongoing study of noncompact manifolds.Comment: This final version will appear in Algebraic & Geometric Topology. Small corrections, including a fix to the statement of Theorem 5.3. 22 pages, 4 figure

Ingestive behaviour and physiology of the medicinal leech

Ingestion lasts 25 min in Hirudo medicinalis and is characterized by pharyngeal peristalsis which fills the crop. This peristalsis has an initial rate of 2.4 Hz which decays smoothly to 1.2 Hz at termination of ingestion. During ingestion, the leech body wall undergoes peristalsis which appears to aid in filling the crop diverticula. Body peristalsis begins at a rate of 10 min^(-1) and decreases linearly to 2 min^(-1) at termination. The body also undergoes dorsoventral flexions when blood flow is occluded. Blood meal size increases slightly with leech size: 8.4 g for 1-g leeches and 9.7 g for 2-g leeches. However, relative meal size decreases markedly with increasing animal size; from 8.15 times body mass for 1-g to 4.80 times for 2-g leeches. When intact leeches were exposed to micromolar concentrations of serotonin, there was an increase in the rate of pharyngeal peristalsis and the size of the blood meals. Leeches excrete the plasma from their ingested blood meals. Excretion is activated during ingestion, which increases feeding efficiency by increasing the proportion of blood cells in the ingestate. Excretion continues for 4–6 days following ingestion, removing all the remaining plasma from the ingestate. Leech ingestion comprises stereotyped muscular movements, secretion of saliva and excretion of plasma. A strikingly similar feeding physiology is seen in the blood-sucking insect Rhodnius, and we suggest that efficient sanguivory may require the convergent evolution of similar ingestive mechanisms

Proteolytic processing and activation of Clostridium perfringens epsilon toxin by caprine small intestinal contents.

Epsilon toxin (ETX), a pore-forming toxin produced by type B and D strains of Clostridium perfringens, mediates severe enterotoxemia in livestock and possibly plays a role in human disease. During enterotoxemia, the nearly inactive ETX prototoxin is produced in the intestines but then must be activated by proteolytic processing. The current study sought to examine ETX prototoxin processing and activation ex vivo using the intestinal contents of a goat, a natural host species for ETX-mediated disease. First, this study showed that the prototoxin has a KEIS N-terminal sequence with a molecular mass of 33,054 Da. When the activation of ETX prototoxin ex vivo by goat small intestinal contents was assessed by SDS-PAGE, the prototoxin was processed in a stepwise fashion into an ~27-kDa band or higher-molecular-mass material that could be toxin oligomers. Purified ETX corresponding to the ~27-kDa band was cytotoxic. When it was biochemically characterized by mass spectrometry, the copresence of three ETX species, each with different C-terminal residues, was identified in the purified ~27-kDa ETX preparation. Cytotoxicity of each of the three ETX species was then demonstrated using recombinant DNA approaches. Serine protease inhibitors blocked the initial proteotoxin processing, while carboxypeptidase inhibitors blocked further processing events. Taken together, this study provides important new insights indicating that, in the intestinal lumen, serine protease (including trypsin and possibly chymotrypsin) initiates the processing of the prototoxin but other proteases, including carboxypeptidases, then process the prototoxin into multiple active and stable species. Importance: Processing and activation by intestinal proteases is a prerequisite for ETX-induced toxicity. Previous studies had characterized the activation of ETX using only arbitrarily chosen amounts of purified trypsin and/or chymotrypsin. Therefore, the current study examined ETX activation ex vivo by natural host intestinal contents. These analyses demonstrated that (i) ETX processing in host intestinal contents occurs in an ordered, stepwise fashion, (ii) processing of prototoxin by host intestinal contents results in higher-molecular-mass material and 3 distinct ~27-kDa ETX species, and (iii) serine proteases, such as trypsin, chymotrypsin, and other proteases, including carboxypeptidases, play a role in the activation of ETX by intestinal contents. These studies provide new insights into the activation and processing of ETX and demonstrate that this process is more complicated than previously appreciated

Consequences of Supergravity with Gauged U(1)R\rm U(1)_R Symmetry

The structure of gauged R supergravity Lagrangians is reviewed, and we consider models with a hidden sector plus light fields of the MSSM. A simple potential for the hidden sector is presented which has a global minimum with zero cosmological constant and spontaneously broken SUSY and R-symmetry. The $\rm U(1)_R$ vector multiplet acquires a Planck scale mass through the Higgs mechanism, and it decouples at low energy. Due to very interesting cancellations, the $\rm U(1)_R$ D-terms also drop out at low energy. Thus no direct effects of the gauging of R-symmetry remain in the low energy effective Lagrangian, and this result is model independent, requiring only that R-symmetry be broken at the Planck scale and $= 0$, where $D$ is the auxiliary field of the $\rm U(1)_R$ vector multiplet. The low energy theory is fairly conventional with soft SUSY breaking terms for the MSSM fields. As a remnant of the gauging of R-symmetry, it also contains light fields, some required to cancel R-anomalies and others from the hidden sector.Comment: 36 pages, plain LaTeX, all macros included, no figure

Senjab v. Alhulaibi, 137 Nev. Adv. Op. 64 (October 21, 2021)

In an opinion drafted by Justice Parraguirre, the Nevada Supreme Court re-evaluated its long holding of the definition of “residence” under Nevada’s divorce statute, NRS 125.020, requiring both physical presence in Nevada (residence) and intent to remain in Nevada. This cas is an appeal of the district court’s dismissal of a divorce complaint for lack of subject-matter jurisdiction due to absence of domicile. The Supreme Court further reviewed its long holding that residence is “synonymous with domicile” for divorce jurisdiction and found its prior rulings were unsound for several reasons. First, NRS 125.020(2) simply and separately addresses “domicile[ ]” in its first clause and “residen[ce]” in its second clause. Given such a construction, the Court could not interpret residence and domicile to be synonymous in NRS 125.020. Also, in Park v. Barr, the Ninth Circuit explained that the California Court of Appeals decision in which the lower court relied “conflated ‘residence’ with ‘domicile’ by describing them as “synonymous.” Furthermore, under NRS 10.155, residence plainly requires only “physical [ ] presen[ce],” not an extra-textual intent to remain. NRS 125.010(1)(e) was satisfied as may obtain divorce in “the district court of any county… if the plaintiff resided 6 weeks in the State before suit was brought. NRS 125.020(2), residence “for a period of not less than 6 weeks preceding the commencement of the action.” In this case, both parties had been physically present in Nevada for at least six weeks before the divorce complaint was filed. The Court found that the district court did not lack subject-matter jurisdiction under NRS 125.020, and reversed and remanded this case