240 research outputs found
Femtosecond Coherent Control of Spin with Light in (Ga,Mn)As ferromagnets
Using density matrix equations of motion, we predict a femtosecond collective
spin tilt triggered by nonlinear, near--ultraviolet (3eV), coherent
photoexcitation of (Ga,Mn)As ferromagnetic semiconductors with linearly
polarized light. This dynamics results from carrier coherences and nonthermal
populations excited in the \{111\} equivalent directions of the Brillouin zone
and triggers a subsequent uniform precession. We predict nonthermal
magnetization control by tuning the laser frequency and polarization direction.
Our mechanism explains recent ultrafast pump--probe experiments.Comment: 4 pages, 3 figures, published in Physical Review Letter
Anomalies of the inferior vena cava: a report of two cases and a short review of the literature
The inferior vena cava, also known as the posterior vena cava, is the large vein
that carries de-oxygenated blood from the lower half of the body into the right
atrium of the heart. Congenital anomalies of the inferior vena cava result from
the persistence of the embryonic venous system. The majority of cases are
clinically silent and are diagnosed in routine dissection studies, in retroperitoneal
surgeries, or through imaging for other reasons. Although these anomalies
are rare, they are of great importance during operations in the abdominal
area or in the treatment of thromboembolic diseases. We report two cases of
double vena cava and left vena cava, respectively, and a short review of the
relevant literature. (Folia Morphol 2010; 69, 3: 123-127
Morphological approach of the sternal foramen: an anatomic study and a short review of the literature
Background: The sternal foramen (SF) constitutes a specific anatomic defect in sternum, indicating an impaired fusion of ossificated segments, which occurs either in an anatomical part of the sternum or in sternal joints. The aim of this article is to provide baseline statistical data about the variations of the SF, to present a short review of the relevant literature and to compare results with other studies and populations.
Materials and methods: We review relevant literature, and we present data obtained from skeletal samples of known population and sex. A total of 35 well-preserved dried sterna from the prefecture of Eastern Macedonia and Thrace, Greece, were selected: 20 men and 15 women with a mean age of 55 ± 6 years old. Measurements were made with a sliding calliper and photographic documentation.
Results: The incidence of the SF in the 35 dried specimens was 14.2%, 4 men (20% of male sample) and 1 woman (6.6% of female sample) and 80% of sternal foramina were observed in male individuals. The SF was found in the sternum body (2 cases, 40% of foramina), in xiphoid process (2 cases, 40% of foramina) and in sternoxiphoidal junction (1 case, 20% of foramina). All of the sterna presented 1 single visible SF. Two anatomically unique cases were identified throughout these 5 sterna, both belonging in male subjects.
Conclusions: The SF constitutes a relatively common variation with great radiological, clinical, and forensic significance. Presence of a SF with irregular bony margins complicates considerably radiological differential diagnosis. Awareness of this important anatomic variation is fundamental for clinicians and autopsy pathologists, in order to avoid severe fatal complications and elucidate the exact cause of death, respectively
All-optical four-state magnetization reversal in (Ga,Mn)As ferromagnetic semiconductors
Using density matrix equations of motion and a tight-binding band
calculation, we predict all-optical switching between four metastable magnetic
states of (III,Mn)As ferromagnets. This switching is initiated non-thermally
within 100fs, during nonlinear coherent photoexcitation. For a single optical
pulse, magnetization reversal is completed after 100 ps and controlled by
the coherent femtosecond photoexcitation. Our predicted switching comes from
magnetic nonlinearities triggered by a femtosecond magnetization tilt that is
sensitive to un--adiabatic light--induced spin interactions.Comment: 3 pages, 2 figures, submitted in Applied Physics Letter
COVID-19 severity and mortality in patients with CLL: an update of the international ERIC and Campus CLL study
Chronic lymphocytic leukemia; Coronavirus infections; MortalityLeucemia linfocítica crónica; Infecciones por coronavirus; MortalidadLeucèmia limfocítica crònica; Infeccions per coronavirus; MortalitatPatients with chronic lymphocytic leukemia (CLL) may be more susceptible to Coronavirus disease 2019 (COVID-19) due to age, disease, and treatment-related immunosuppression. We aimed to assess risk factors of outcome and elucidate the impact of CLL-directed treatments on the course of COVID-19. We conducted a retrospective, international study, collectively including 941 patients with CLL and confirmed COVID-19. Data from the beginning of the pandemic until March 16, 2021, were collected from 91 centers. The risk factors of case fatality rate (CFR), disease severity, and overall survival (OS) were investigated. OS analysis was restricted to patients with severe COVID-19 (definition: hospitalization with need of oxygen or admission into an intensive care unit). CFR in patients with severe COVID-19 was 38.4%. OS was inferior for patients in all treatment categories compared to untreated (p < 0.001). Untreated patients had a lower risk of death (HR = 0.54, 95% CI:0.41-0.72). The risk of death was higher for older patients and those suffering from cardiac failure (HR = 1.03, 95% CI:1.02-1.04; HR = 1.79, 95% CI:1.04-3.07, respectively). Age, CLL-directed treatment, and cardiac failure were significant risk factors of OS. Untreated patients had a better chance of survival than those on treatment or recently treated
Finite SU(N)^k Unification
We consider N=1 supersymmetric gauge theories based on the group SU(N)_1 x
SU(N)_2 x ... x SU(N)_k with matter content (N,N*,1,...,1) + (1,N,N*,...,1) +
>... + (N*,1,1,...,N) as candidates for the unification symmetry of all
particles. In particular we examine to which extent such theories can become
finite and we find that a necessary condition is that there should be exactly
three families. We discuss further some phenomenological issues related to the
cases (N,k) = (3,3), (3,4), and (4,3), in an attempt to choose those theories
that can become also realistic. Thus we are naturally led to consider the
SU(3)^3 model which we first promote to an all-loop finite theory and then we
study its additional predictions concerning the top quark mass, Higgs mass and
supersymmetric spectrum.Comment: 15 page
Dynamical generation of fuzzy extra dimensions, dimensional reduction and symmetry breaking
We present a renormalizable 4-dimensional SU(N) gauge theory with a suitable
multiplet of scalar fields, which dynamically develops extra dimensions in the
form of a fuzzy sphere S^2. We explicitly find the tower of massive
Kaluza-Klein modes consistent with an interpretation as gauge theory on M^4 x
S^2, the scalars being interpreted as gauge fields on S^2. The gauge group is
broken dynamically, and the low-energy content of the model is determined.
Depending on the parameters of the model the low-energy gauge group can be
SU(n), or broken further to SU(n_1) x SU(n_2) x U(1), with mass scale
determined by the size of the extra dimension.Comment: 27 pages. V2: discussion and references added, published versio
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