6 research outputs found
Comparison of relativity theories with observer-independent scales of both velocity and length/mass
We consider the two most studied proposals of relativity theories with
observer-independent scales of both velocity and length/mass: the one discussed
by Amelino-Camelia as illustrative example for the original proposal
(gr-qc/0012051) of theories with two relativistic invariants, and an
alternative more recently proposed by Magueijo and Smolin (hep-th/0112090). We
show that these two relativistic theories are much more closely connected than
it would appear on the basis of a naive analysis of their original
formulations. In particular, in spite of adopting a rather different formal
description of the deformed boost generators, they end up assigning the same
dependence of momentum on rapidity, which can be described as the core feature
of these relativistic theories. We show that this observation can be used to
clarify the concepts of particle mass, particle velocity, and
energy-momentum-conservation rules in these theories with two relativistic
invariants.Comment: 21 pages, LaTex. v2: Andrea Procaccini (contributing some results
from hia Laurea thesis) is added to the list of authors and the paper
provides further elements of comparison between DSR1 and DSR2, including the
observation that both lead to the same formula for the dependence of momentum
on rapidit
A Geometric Approach to Trajectory Design for an Autonomous Underwater Vehicle: Surveying the Bulbous Bow of a Ship
The reduction of selenium(IV) by hydrogen sulfide in aqueous solutions
The rates for the reduction of Se(IV) by sulfides were measured in NaCl solutions as a function of pH (2-10), temperature (10-40°C) and ionic strength (I=0.01-1M). The pseudo first-order rate constant (logk 1) showed a complex dependence on pH with values decreasing from pH 2 to a minimum at pH 4.5, then increasing from pH 5.5 to a maximum near pH 8 and decreasing again at pH higher than 8. The values of the overall kinetic constant (k) calculated from the values of k 1/[H 2S] T can be determined from equations: logk=-0.15pH-1355.5/T+0.44I0.5+7.74 for the pH range 2-4.5 (Ï=±0.16), logk=0.28pH-1090.9/T+0.60I0.5+4.68 for the pH range 5.5-7.6 (Ï=±0.10) and logk=-0.50pH-1572.1/T+0.45I0.5+12.67 for the pH range 7.7-10 (Ï=±0.05), from 10 to 40°C and from 0.01 to 1M ionic strength. The effect of pH and ionic strength on the reaction suggests that the reactions in natural waters are due to the following interactions: H2SeO3+H2Sâproducts HSeO3-+H2Sâproducts HSeO3-+HS-âproducts while under strong alkaline conditions (pH>9) a fourth contribution by SeO32-+HS-âproducts is also possible. The overall rate expression over the entire pH range investigated can be determined from (H 2A=H 2SeO 3; HA=HSeO 3 -; A=SeO 3 2-) k=(kH2S-H2A[H+]3+kH2S-HAKHA[H+]2+kHS-HAKHAK1s[H+]+kHS-AKHAKAK1s)/{([H+]2+KHA[H+]+KAKHA)([H+]+K1s)} where kH2S-H2A=2409±566M-1min-1, kH2S-HA=464±233M-1min-1, k HS-HA=4190±573M -1min -1 and k HS-A=650±382M -1min -1 and K HA, K A and K 1s are the dissociation constants of selenous acid and hydrogen sulfide. Kinetic runs in natural freshwater samples and natural seawater have confirmed results obtained in simple NaCl solutions suggesting that this reaction may play an important role under anoxic and hypoxic conditions. Sulfide concentrations under these conditions may range from micromolar to millimolar level and Se(IV) half times are in the order of a few hours to minutes, respectively. © 2011 Elsevier Ltd
COVID-19-related death in patients with alcohol or substance use disorders.
BACKGROUND People with substance or alcohol use disorders (SUDs/AUDs) are likely to be more vulnerable to COVID-19 infection than the general population, but the evidence of COVID-19-related mortality in these patients is unclear.
OBJECTIVES The aim of the study was to verify whether patients with AUD and SUD have a higher mortality rate for COVID-19-related mortality compared to the general population.
METHOD We performed a follow-up study to assess mortality in 2020 in a cohort of patients diagnosed for the first time with AUDs or SUDs at the Public Health Services in the metropolitan area of Bologna (Northern Italy) from 2009 to 2019.
RESULTS SUDs/AUDs patients present an excess mortality with respect to the general population for all causes of death and for COVID-19-related mortality.
CONCLUSIONS Our data support the need for prevention strategies in SUDs/AUDs patients such as vaccinations
Lâunica riforma necessaria per il Mes
LâItalia eÌ rimasto il solo paese a non aver sottoscritto la riforma del Meccanismo europeo di stabilitaÌ (Mes) e si moltiplicano le pressioni, interne ed esterne, percheÌ provveda a farlo
Mes, una riforma che persevera negli errori. Un appello di economisti e giuristi
LâItalia non deve avallare un meccanismo che riproduce le logiche del passato, che si sono rivelate clamorosamente sbagliate. Inoltre accettare questa riforma significherebbe ridurre gli interventi innovativi decisi per fronteggiare la pandemia a unâeccezione, in attesa di tornare appena possibile a politiche che minacciano la stessa sopravvivenza dellâUnione