7,927 research outputs found
Litigation risks and firms innovation dynamics after the IPO
An initial public offering (IPO) is a critical event in a firm’s life cycle which can reshape its innovation strategy. Research suggests that after going public firms experience an increase in patent productivity. Our paper explores perceived litigation risks as a determinant of this outcome by examining US semiconductor firms. Results show that perceived patent litigation risks are positively associated with patent productivity after the IPO. Interestingly, we also find that the amount of capital raised during the IPO is positively associated with patent productivity after the IPO, successfully replicating previous findings on this relationship. These results are robust to model specifications where we attempt to account for the dynamics of self-selection of firms into IPO by considering matched control firms with similar pre-IPO characteristics, but that never went public
Association of early glycemic change with short-term mortality in lobar and non-lobar intracerebral hemorrhage
The association between early glycemic change and short-term mortality in non-diabetic patients with acute intracerebral hemorrhage (ICH) is unclear. We retrospectively investigated non-diabetic patients with lobar (n = 262) and non-lobar ICH (n = 370). Each patient had a random serum glucose test on hospital admission and a fasting serum glucose test within the following 48 h. Hyperglycemia was defined as serum glucose ≥ 7.8 mmol/l. Four patterns were determined: no hyperglycemia (reference category), persistent hyperglycemia, delayed hyperglycemia, and decreasing hyperglycemia. Associations with 30-day mortality were estimated using Cox models adjusted for major features of ICH severity. Persistent hyperglycemia was associated with 30-day mortality in both lobar (HR 3.00; 95% CI 1.28-7.02) and non-lobar ICH (HR 4.95; 95% CI 2.20-11.09). In lobar ICH, 30-day mortality was also associated with delayed (HR 4.10; 95% CI 1.77-9.49) and decreasing hyperglycemia (HR 2.01, 95% CI 1.09-3.70). These findings were confirmed in Cox models using glycemic change (fasting minus random serum glucose) as a continuous variable. Our study shows that, in non-diabetic patients with ICH, early persistent hyperglycemia is an independent predictor of short-term mortality regardless of hematoma location. Moreover, in non-diabetic patients with lobar ICH, both a positive and a negative glycemic change are associated with short-term mortality
Combined observations of meteors by image-orthicon television camera and multi-station radar
Observations from multiple sites of a radar network and by television of 29 individual meteors from February 1969 through June 1970 are reported. Only 12 of the meteors did not appear to fragment over all the observed portion of their trajectories. From these 12, the relation for the radar magnitude to the panchromatic absolute magnitude was found in terms of velocity of the meteor. A very tentative fit to the data on the duration of long enduring echoes versus visual absolute magnitude is made. The exponential decay characteristics of the later parts of several of the light curves are pointed out as possible evidence of mutual coalescence of droplets into which the meteoroid has completely broken
Devices based on 2D materials for on-chip amplification of ionization charges
Pixels detectors are widely used ionizing radiation detection devices in high-energy physics (HEP)experiments. Segmented detectors have been employed for many years due to the need to simul-taneously track the thousands of particles emerging from modern colliders. For more preciseand accurate measurements one would like to have faster, less noisy and smaller pixels, but cur-rent technology imposes several limits on these characteristics. The aim of this work is to ex-plore the possible applications of bi-dimensional materials such as Graphene or transition metaldichalcogenide monolayers (TMDs) to address these problems. In particular, one wants to de-termine whether nano-electronic devices based on 2D materials could be used to obtain built-inpre-amplification of the pixel signal, thus achieving better detection performance. The workingprinciple is the field-effect modulation of the channel conductivity in a 2D material-based tran-sistor, due to the presence of ionization charges in a silicon absorber. Several architectures aretested, and a final device of choice is presented, with a sketch of a realistic readout system andits noise figure. The conductance modulation due to incoming particles is found to be more than30%, resulting in a strong current signal, which leads to very favourable signal-to-noise ratios (SNR)
Direct evidence for efficient ultrafast charge separation in epitaxial WS/graphene heterostructure
We use time- and angle-resolved photoemission spectroscopy (tr-ARPES) to
investigate ultrafast charge transfer in an epitaxial heterostructure made of
monolayer WS and graphene. This heterostructure combines the benefits of a
direct gap semiconductor with strong spin-orbit coupling and strong
light-matter interaction with those of a semimetal hosting massless carriers
with extremely high mobility and long spin lifetimes. We find that, after
photoexcitation at resonance to the A-exciton in WS, the photoexcited holes
rapidly transfer into the graphene layer while the photoexcited electrons
remain in the WS layer. The resulting charge transfer state is found to
have a lifetime of \,ps. We attribute our findings to differences in
scattering phase space caused by the relative alignment of WS and graphene
bands as revealed by high resolution ARPES. In combination with spin-selective
excitation using circularly polarized light the investigated WS/graphene
heterostructure might provide a new platform for efficient optical spin
injection into graphene.Comment: 28 pages, 14 figure
Microalgae potential in the capture of CO2 emission
In a perspective projected to reduce the atmospheric concentration of greenhouse gases, in which carbon dioxide is the master, the use of microalgae is an effective and decisive response. The review describes the bio circularity of the process of abatement of carbon dioxide through biofixation in algal biomass, highlighting the potential of its reuse in the production of high value-added products
Direct evidence for efficient ultrafast charge separation in epitaxial WS<sub>2</sub>/graphene heterostructures
We use time- and angle-resolved photoemission spectroscopy (tr-ARPES) to investigate ultrafast charge transfer in an epitaxial heterostructure made of monolayer WS2 and graphene. This heterostructure combines the benefits of a direct-gap semiconductor with strong spin-orbit coupling and strong light-matter interaction with those of a semimetal hosting massless carriers with extremely high mobility and long spin lifetimes. We find that, after photoexcitation at resonance to the A-exciton in WS2, the photoexcited holes rapidly transfer into the graphene layer while the photoexcited electrons remain in the WS2 layer. The resulting charge-separated transient state is found to have a lifetime of ∼1 ps. We attribute our findings to differences in scattering phase space caused by the relative alignment of WS2 and graphene bands as revealed by high-resolution ARPES. In combination with spin-selective optical excitation, the investigated WS2/graphene heterostructure might provide a platform for efficient optical spin injection into graphene
L’ambiente carsico e l’idrogeologia dei gessi di Sassalbo (MS)
Nel Canale dell’Acqua Torbida (Alta Lunigiana), si trova
il maggiore affioramento di evaporiti triassiche della Toscana.
Rispetto ai gessi dell’Alta val Secchia (RE), di cui
sono il lembo meridionale, appaiono molto meno tettonizzati.
L’area carsica, che comprende in prevalenza calcari
cavernosi, ha una superficie complessiva di circa 2,2 km2
in cui sono ben rappresentate forme carsiche superficiali,
sia macro che micro. Anche i fenomeni carsici sotterranei
sembrano essere ben sviluppati: la loro genesi è stata attribuita
a periodi di avanzata e arretramento dei ghiacciai
durante l’ultimo glaciale. Attualmente nel catasto toscano
sono registrate 5 cavità , di cui 4 rilevate.
Nell’ambito del Progetto Trias II (studio interdisciplinare
svolto dalla Società Speleologica Italiana per conto del
Parco Nazionale dell’Appennino Tosco-Emiliano) è stato
possibile studiare l’area dal punto di vista morfologico,
speleologico e idrochimico, monitorando in continuo alcune
delle principali risorgenti carsiche parallelamente ai
torrenti cui esse potevano risultare connesse.
Nel presente lavoro, dopo breve illustrazione delle morfologie
epigee ed ipogee, vengono presentati i risultati del
monitoraggio idrologico. Le analisi hanno permesso di
evidenziare come in molti casi le acque del carso di Sassalbo
siano chimicamente molto simili a quelle del sistema
ad ansa ipogea del Tanone della Gacciolina in Alta val di
Secchia. Fanno eccezione altre sorgenti, alimentate quasi
esclusivamente dalla serie marnoso arenacea e dal macigno,
che presentano comportamenti idrodinamici differenti
in funzione dei loro specifici bacini di alimentazione.Karst and hydrology of the Sassalbo Gypsa (Massa Carrara
– Italy)
The largest triassic evaporitic outcrop of Tuscany is located
inside the Acqua Torbida creek (Upper Lunigiana).
They represent the southernmost and less tectonized part
of the Upper Secchia Gypsa (RE). The karst area (some 2,2)
consists mostly of limestone (Calcari Cavernosi) with well
developed macro – and micro – forms. The underground
phenomena are mainly related to the mouventes of glacial
tongues during the last Glacial. 5 cavities are presently
known and inserted in the Tuscany Cadaster, 4 of which
mapped. In the framework of the Trias II Project (an interdisciplinary
study sponsored by the Appennino Tosco-Emiliano
National Park and performed by the Italian Speleological
Society) this area has been investigated from the
morphological, speleological, hydrochemical point of view
while some of the major springs and related rivers were
monitored. In the paper after a short description of the epigean
and hypogean forms, the achieved result during the
hydrological study are presented. This study evidenced
that in many occurrences the behavior of the Sassalbo
karst waters is very similar to that of the Tanone della Gacciolina
cave in the Upper Secchia Valley. Only a few springs
exhibit a different behavior being rather completely fed
by the marnoso-arenacea and macigno formations
Theoretical status of Bs-mixing and lifetimes of heavy hadrons
We review the theoretical status of the lifetime ratios τB+/τBd, τBs/τBd, τΛb/τBd and τBc and of the mixing quantities ΔMs, ΔΓs and ϕs. ΔMs and ΔΓs suffer from large uncertainties due to the badly known decay constants, while the ratio ΔΓs/ΔMs can be determined with almost no non-perturbative uncertainties, therefore it can be used perfectly to find possible new physics contributions in the mixing parameters. We suggest a very clear method of visualizing the bounds on new physics and demonstrate this by combining the latest experimental numbers on the mixing quantities quantities with theory – one already gets some hints for new physics contributions, but more precise experimental numbers are needed to draw some definite conclusions. We conclude with a ranking list of all the discussed quantities according to their current theoretical uncertainties and point out possible improvements
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