1,194 research outputs found
Search for X-ray emission from subdwarf B stars with compact companion candidates
Stellar evolutionary models predict that most of the early type subdwarf
stars in close binary systems have white dwarf companions. More massive
companions, such as neutron stars or black holes, are also expected in some
cases. The presence of compact stars in these systems can be revealed by the
detection of X-rays powered by accretion of the subdwarf's stellar wind or by
surface thermal emission. Using the Swift satellite, we carried out a
systematic search for X-ray emission from a sample of twelve subdwarf B stars
which, based on optical studies, have been suggested to have degenerate
companions. None of our targets was detected, but the derived upper limits
provide one of the few observational constraints on the stellar winds of early
type subdwarfs. If the presence of neutron star companions is confirmed, our
results constrain the mass loss rates of some of these subdwarf B stars to
values <10^{-13}-10^{-12} Msun/yr.Comment: Accepted for publication in Astronomy and Astrophysic
Smart Bulbs can be Hacked to Hack into your Household
The IoT is getting more and more pervasive. Even the simplest devices, such
as a light bulb or an electrical plug, are made "smart" and controllable by our
smartphone. This paper describes the findings obtained by applying the PETIoT
kill chain to conduct a Vulnerability Assessment and Penetration Testing
session on a smart bulb, the Tapo L530E by Tp-Link, currently best seller on
Amazon Italy. We found that four vulnerabilities affect the bulb, two of High
severity and two of Medium severity according to the CVSS v3.1 scoring system.
In short, authentication is not well accounted for and confidentiality is
insufficiently achieved by the implemented cryptographic measures. In
consequence, an attacker who is nearby the bulb can operate at will not just
the bulb but all devices of the Tapo family that the user may have on her Tapo
account. Moreover, the attacker can learn the victim's Wi-Fi password, thereby
escalating his malicious potential considerably. The paper terminates with an
outline of possible fixes
The interaction of droplet dynamics and turbulence cascade
The dynamics of droplet fragmentation in turbulence is described by the Kolmogorov-Hinze framework. Yet, a quantitative theory is lacking at higher concentrations when strong interactions between the phases and coalescence become relevant, which is common in most flows. Here, we address this issue through a fully-coupled numerical study of the droplet dynamics in a turbulent flow at R-lambda & AP; 140, the highest attained up to now. By means of time-space spectral statistics, not currently accessible to experiments, we demonstrate that the characteristic scale of the process, the Hinze scale, can be precisely identified as the scale at which the net energy exchange due to capillarity is zero. Droplets larger than this scale preferentially break up absorbing energy from the flow; smaller droplets, instead, undergo rapid oscillations and tend to coalesce releasing energy to the flow. Further, we link the droplet-size distribution with the probability distribution of the turbulent dissipation. This shows that key in the fragmentation process is the local flux of energy which dominates the process at large scales, vindicating its locality
Emergency decompressive craniectomy after removal of convexity meningiomas
BACKGROUND: Convexity meningiomas are benign brain tumors that are amenable to complete surgical resection and are associated with a low complication rate. The aim of this study was to identify factors that result in acute postoperative neurological worsening after the removal of convexity meningiomas. METHODS: Clinical evaluation and neuroradiological analysis of patients who underwent removal of a supratentorial convexity meningioma were reviewed. Patients were selected when their postoperative course was complicated by acute neurological deterioration requiring decompressive craniectomy. RESULTS: Six patients (mean age: 43.3 years) underwent surgical removal of a supratentorial convexity meningioma. Brain shift (mean: 9.9 mm) was evident on preoperative imaging due to lesions of varying size and perilesional edema. At various times postoperatively, patient consciousness worsened (up to decerebrate posture) with contralateral paresis and pupillary anisocoria. Computed tomography revealed no postoperative hematoma, however, did indicate increased brain edema and ventricular shift (mean: 12 mm). Emergency decompressive craniectomy and brief ventilator assistance were performed in all patients. Ischemia of the ipsilateral posterior cerebral artery occurred in 3 patients and hydrocephalus occurred in 2 patients. Outcome was good in 2, fair in 2, 1 patient had severe disability, and 1 patient died after 8 months. CONCLUSIONS: Brain shift on preoperative imaging is a substantial risk factor for postoperative neurological worsening in young adult patients after the removal of convexity meningiomas. Emergency decompressive craniectomy must be considered because it is effective in most cases. Other than consciousness impairment, there is no reliable clinical landmark to guide the decision to perform decompressive craniectomy; however, brain ischemia may have already occurred
Poaceae vs. Abiotic stress: Focus on drought and salt stress, recent insights and perspectives
Poaceae represent the most important group of crops susceptible to abiotic stress. This large family of monocotyledonous plants, commonly known as grasses, counts several important cultivated species, namely wheat (Triticum aestivum), rice (Oryza sativa), maize (Zea mays), and barley (Hordeum vulgare). These crops, notably, show different behaviors under abiotic stress conditions: wheat and rice are considered sensitive, showing serious yield reduction upon water scarcity and soil salinity, while barley presents a natural drought and salt tolerance. During the green revolution (1940–1960), cereal breeding was very successful in developing high-yield crops varieties; however, these cultivars were maximized for highest yield under optimal conditions, and did not present suitable traits for tolerance under unfavorable conditions. The improvement of crop abiotic stress tolerance requires a deep knowledge of the phenomena underlying tolerance, to devise novel approaches and decipher the key components of agricultural production systems. Approaches to improve food production combining both enhanced water use efficiency (WUE) and acceptable yields are critical to create a sustainable agriculture in the future. This paper analyzes the latest results on abiotic stress tolerance in Poaceae. In particular, the focus will be directed toward various aspects of water deprivation and salinity response efficiency in Poaceae. Aspects related to cell wall metabolism will be covered, given the importance of the plant cell wall in sensing environmental constraints and in mediating a response; the role of silicon (Si), an important element for monocots' normal growth and development, will also be discussed, since it activates a broad-spectrum response to different exogenous stresses. Perspectives valorizing studies on landraces conclude the survey, as they help identify key traits for breeding purposes
Mechanism(s) of action of heavy metals to investigate the regulation of plastidic glucose-6-phosphate dehydrogenase
The regulation of recombinant plastidic glucose-6P dehydrogenase from Populus trichocarpa (PtP2-G6PDH - EC 1.1.1.49) was investigated by exposing wild type and mutagenized isoforms to heavy metals. Nickel and Cadmium caused a marked decrease in PtP2-G6PDH WT activity, suggesting their poisoning effect on plant enzymes; Lead (Pb++) was substantially ineffective. Copper (Cu++) and Zinc (Zn++) exposition resulted in strongest decrease in enzyme activity, thus suggesting a physiological competition with Magnesium, a well-known activator of G6PDH activity. Kinetic analyses confirmed a competitive inhibition by Copper, and a mixed inhibition by (Cd++). Mutagenized enzymes were differently affected by HMs: the reduction of disulfide (C175-C183) exposed the NADP+ binding sites to metals; C145 participates to NADP+ cofactor binding; C194 and C242 are proposed to play a role in the regulation of NADP+/NADPH binding. Copper (and possibly Zinc) is able to occupy competitively Magnesium (Mg++) sites and/or bind to NADP+, resulting in a reduced access of NADP+ sites on the enzyme. Hence, heavy metals could be used to describe specific roles of cysteine residues present in the primary protein sequence; these results are discussed to define the biochemical mechanism(s) of inhibition of plant plastidic G6PDH
High-yield fabrication of entangled photon emitters for hybrid quantum networking using high-temperature droplet epitaxy
Several semiconductor quantum dot techniques have been investigated for the
generation of entangled photon pairs. Among the other techniques, droplet
epitaxy enables the control of the shape, size, density, and emission
wavelength of the quantum emitters. However, the fraction of the
entanglement-ready quantum dots that can be fabricated with this method is
still limited to around 5%, and matching the energy of the entangled photons to
atomic transitions (a promising route towards quantum networking) remains an
outstanding challenge.
Here, we overcome these obstacles by introducing a modified approach to
droplet epitaxy on a high symmetry (111)A substrate, where the fundamental
crystallization step is performed at a significantly higher temperature as
compared to previous reports. Our method drastically improves the yield of
entanglement-ready photon sources near the emission wavelength of interest,
which can be as high as 95% due to the low values of fine structure splitting
and radiative lifetime, together with the reduced exciton dephasing offered by
the choice of GaAs/AlGaAs materials. The quantum dots are designed to emit in
the operating spectral region of Rb-based slow-light media, providing a viable
technology for quantum repeater stations.Comment: 14 pages, 3 figure
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