An Optimal Medium Access Control with Partial Observations for Sensor Networks

We consider medium access control (MAC) in multihop sensor networks, where only partial information about the shared medium is available to the transmitter. We model our setting as a queuing problem in which the service rate of a queue is a function of a partially observed Markov chain representing the available bandwidth, and in which the arrivals are controlled based on the partial observations so as to keep the system in a desirable mildly unstable regime. The optimal controller for this problem satisfies a separation property: we first compute a probability measure on the state space of the chain, namely the information state, then use this measure as the new state on which the control decisions are based. We give a formal description of the system considered and of its dynamics, we formalize and solve an optimal control problem, and we show numerical simulations to illustrate with concrete examples properties of the optimal control law. We show how the ergodic behavior of our queuing model is characterized by an invariant measure over all possible information states, and we construct that measure. Our results can be specifically applied for designing efficient and stable algorithms for medium access control in multiple-accessed systems, in particular for sensor networks

Spectral properties of the largest asteroids associated with Taurid Complex

We obtained spectra of six of the largest asteroids (2201, 4183, 4486, 5143, 6063, and 269690) associated with Taurid complex. The observations were made with the IRTF telescope equipped with the spectro-imager SpeX. Their taxonomic classification is made using Bus-DeMeo taxonomy. The asteroid spectra are compared with the meteorite spectra from the Relab database. Mineralogical models were applied to determine their surface composition. All the spectral analysis is made in the context of the already published physical data. Five of the objects studied in this paper present spectral characteristics similar to the S taxonomic complex. The spectra of ordinary chondrites (spanning H, L, and LL subtypes) are the best matches for these asteroid spectra. {\bf The asteroid} (269690) 1996 RG3 presents a flat featureless spectrum which could be associated to a primitive C-type object. The increased reflectance above 2.1 microns constrains its geometrical albedo to a value around 0.03. While there is an important dynamical grouping among the Taurid Complex asteroids, the spectral data of the largest objects do not support a common cometary origin. Furthermore, there are significant variations between the spectra acquired until now.Comment: Accepted for publication in A&

Intriguing behavior when testing the impact of quotation marks usage in Google search results

Internet research on search engine quality and validity of results demand much concern. Thus, the focus in our study has been to measure the impact of quotation marks usage on the internet search outputs in terms of Google search outcomes’ distributions, through Benford Law. The current paper is focused on applying a Benford Law analysis on two related types of internet searches distinguished by the usage or absence of quotation marks. Both search results values are assumed as variables. We found that the first digit of outcomes does not follow the Benford Law first digit of numbers in the case of searching text without quotation marks. Unexpectedly, the Benford Law is obeyed when quotation marks are used, even if the variability of search outcomes is considerably reduced. By studying outputs demonstrating influences of (apparently at first) “details”, in using a search engine, the authors are able to further warn the users concerning the validity of such outputs. This is a post-peer-review, pre-copyedit version of an article published in Quality & Quantity. The final authenticated version is available online at: http://dx.doi.org/10.1007/s11135-018-0771-

Cryogenic bath-type heat exchangers for ultra-pure noble gas applications

Two cryogenic bath-type heat exchangers for ultra-pure noble gas applications were developed with particular emphasis on noble gas liquefaction in cryogenic distillation systems. The main objective was to construct heat exchangers for xenon from materials that do not emanate radon and that fulfill ultra-high vacuum standards. Therefore, only high-quality copper and stainless steel materials were used. Especially, large-area oxygen-free copper fins with high conductivity in a new design ensure efficient heat transfer. One bath-type Xe-Xe heat exchanger was designed with a diameter of 50 cm to achieve a xenon condensing capacity of at least 100 kg/h. In order to guarantee the necessary heat transfer between the two xenon reservoirs, this heat exchanger features a specially manufactured stainless steel flange with a copper plate welded inside. We first tested our concept on a dedicated bath-type heat exchanger with a reduced diameter of 30 cm using liquid nitrogen to liquefy the xenon. A model based on conservative assumptions such as film boiling on the nitrogen side and film condensation on the xenon side was developed and applied to caluclate the expected heat transfer for our design. We were able to demonstrate an adjustable xenon liquefaction rate of up to 113 kg/h limited only by our measurement procedure at a cooling efficiency of (0.98 ± 0.03) for the LN$_{2}$-Xe heat exchanger

Taxonomic classification of asteroids based on MOVIS near-infrared colors

We aim to provide a taxonomic classification for asteroids observed by VISTA-VHS survey. We derive a method for assigning a compositional type to an object based on its (Y-J), (J-Ks), and (H-Ks) colors. We present a taxonomic classification for 18\,265 asteroids from the MOVIS catalog, using a probabilistic method and the k-nearest neighbors algorithm. Because our taxonomy is based only on NIR colors, several classes from Bus-DeMeo were clustered into groups and a slightly different notation was used (i.e. the superscript indicates that the classification was obtained based on the NIR colors and the subscript indicates possible miss-identifications with other types). Our results are compared with the information provided by the Sloan Digital Sky Survey (SDSS) and Wide-field Infrared Survey Explorer (WISE). The two algorithms used in this study give a taxonomic type for all objects having at least (Y-J) and (J-Ks) observed colors. A final classification is reported for a set of 6\,496 asteroids based on the criteria that KNN and probabilistic algorithms gave the same result, (Y-J)$_{err}\leq$ 0.118 and (J-Ks)$_{err}\leq$0.136. This set includes 144 bodies classified as $B_k^{ni}$, 613 as $C^{ni}$, 197 as $C_{gx}^{ni}$, 91 as $X_t^{ni}$, 440 as $D_s^{ni}$, 665 as $K_l^{ni}$, 233 as $A_d^{ni}$, 3\,315 as $S^{ni}$, and 798 as $V^{ni}$. We report the albedo distribution for each taxonomic group and we compute new median values for the main types. We found that V-type and A-type candidates have identical size frequency distributions, but the V-types are five times more common than the A-types. Several particular cases, such as the A-type asteroid (11616) 1996 BQ2 and the S-type (3675) Kematsch, both in the Cybele population, are discussed. Files and codes available at: https://github.com/marcelpopescu/MOVIS-TaxonomyComment: 18 pages, 10 figures, accepted for publication in Astronomy & Astrophysics (A&A

Cross-continental emergence of Nannizziopsis barbatae disease may threaten wild Australian lizards

Members of the genus Nannizziopsis are emerging fungal pathogens of reptiles that have been documented as the cause of fatal mycoses in a wide range of reptiles in captivity. Cases of severe, proliferative dermatitis, debility and death have been detected in multiple free-living lizard species from locations across Australia, including a substantial outbreak among Eastern water dragons (Intellagama lesueurii) in Brisbane, Queensland. We investigated this disease in a subset of severely affected lizards and identified a clinically consistent syndrome characterized by hyperkeratosis, epidermal hyperplasia, dermal inflammation, necrosis, ulceration, and emaciation. Using a novel fungal isolation method, histopathology, and molecular techniques, we identified the etiologic agent as Nannizziopsis barbatae, a species reported only once previously from captive lizards in Australia. Here we report severe dermatomycosis caused by N. barbatae in five species of Australian lizard, representing the first cases of Nannizziopsis infection among free-living reptiles, globally. Further, we evaluate key pathogen and host characteristics that indicate N. barbatae-associated dermatomycosis may pose a concerning threat to Australian lizards

Statin therapy in patients with diabetes and hepatitis C

The objective of this study was to determine the effects of statin therapy (atorvastatin) on serum aspartate aminotransferase (AST) and alanine aminotransferase (ALT) levels in patients with type 2 diabetes mellitus (T2DM) and chronic hepatitis C (CHC). A number of 77 patients with T2DM and CHC were selected, treated with atorvastatin, 20 mg, for 6 months, who underwent anthropometric measurements and biochemical tests (including fasting serum glucose, lipid profile, liver profile, cytokines profile) at baseline, after 1 month (clinical and biochemical profile for safety) and after 6 months of treatment. The patients’ average age was 52.53±9.7 years. Plasma low-density lipoprotein cholesterol (LDL-C) (-32.4 mg/dL), triglycerides (-29.7 mg/dL), total cholesterol (-32.8 mg/dL) decreased (p<0.05), and high-density lipoprotein cholesterol (HDL-C) (+3.04 mg/dL) increased (p<0.05), after 6 months. Atorvastatin treatment was associated with decreases of AST, ALT, and also leptin and interleukin-6 (IL-6) levels (all p<0.05) but we did not find any effect on plasma tumor necrosis factor-alpha (TNF-α) (p=0.119). Atorvastatin was an effective and well tolerated treatment for lowering total cholesterol, LDL-C, triglycerides in patients with CHC. Among patients with CHC there was no significant elevation of liver enzymes during statin treatment, and we even noticed an improvement of hepatic profile