Signatures of the Optical Stark Effect on Entangled Photon Pairs from Resonantly Pumped Quantum Dots.

Two-photon resonant excitation of the biexciton-exciton cascade in a quantum dot generates highly polarization-entangled photon pairs in a near-deterministic way. However, the ultimate level of achievable entanglement is still debated. Here, we observe the impact of the laser-induced ac-Stark effect on the quantum dot emission spectra and on entanglement. For increasing pulse-duration-to-lifetime ratios and pump powers, decreasing values of concurrence are recorded. Nonetheless, additional contributions are still required to fully account for the observed below-unity concurrence.

Measured proton electromagnetic structure deviates from theoretical predictions.

The visible world is founded on the proton, the only composite building block of matter that is stable in nature. Consequently, understanding the formation of matter relies on explaining the dynamics and the properties of the proton's bound state. A fundamental property of the proton involves the response of the system to an external electromagnetic field. It is characterized by the electromagnetic polarizabilities1 that describe how easily the charge and magnetization distributions inside the system are distorted by the electromagnetic field. Moreover, the generalized polarizabilities2 map out the resulting deformation of the densities in a proton subject to an electromagnetic field. They disclose essential information about the underlying system dynamics and provide a key for decoding the proton structure in terms of the theory of the strong interaction that binds its elementary quark and gluon constituents. Of particular interest is a puzzle in the electric generalized polarizability of the proton that remains unresolved for two decades2. Here we report measurements of the proton's electromagnetic generalized polarizabilities at low four-momentum transfer squared. We show evidence of an anomaly to the behaviour of the proton's electric generalized polarizability that contradicts the predictions of nuclear theory and derive its signature in the spatial distribution of the induced polarization in the proton. The reported measurements suggest the presence of a new, not-yet-understood dynamical mechanism in the proton and present notable challenges to the nuclear theory.

Effects of nutrient restriction and melatonin supplementation from mid-to-late gestation on maternal and fetal small intestinal carbohydrase activities in sheep.

The objective of this experiment was to evaluate the effects of nutrient restriction and melatonin supplementation during mid-to-late gestation on maternal and fetal small intestinal carbohydrase activities in sheep. Ewes were randomly assigned to one of 4 dietary treatments arranged in a 2 × 2 factorial design. Ewes were fed to provide 100% (adequate; ADQ) or 60% (restricted; RES) of nutrient recommendations, and diets were supplemented with either no melatonin (control; CON) or 5 mg melatonin/d (melatonin; MEL). This resulted in 4 treatment groups: CON-ADQ (n = 7), CON-RES (n = 8), MEL-ADQ (n = 8), MEL-RES (n = 8). Treatments began on day 50 of gestation, and ewes were euthanized on day 130 for tissue collection. The maternal and fetal small intestine were collected and assayed for small intestinal carbohydrase activities. Data were analyzed using the GLM procedure of SAS with fetal sex, melatonin, nutrition, and the melatonin by nutrition interaction included in the model statement. There were no melatonin by nutrition interactions for maternal or fetal small intestinal protein concentration or carbohydrase activities (P ≥ 0.11). Dietary melatonin supplementation decreased (P = 0.03) maternal small intestinal protein concentration by 22.7% and increased (P = 0.03) maternal small intestinal glucoamylase, isomaltase, and maltase activity per gram protein by 45.5%, 41.3%, and 40.6%, respectively. Nutrient restriction from mid-to-late gestation did not influence (P ≥ 0.46) maternal small intestinal protein concentration, or maltase, isomaltase, and lactase activity. Maternal glucoamylase activity per gram intestine increased (P = 0.05) with nutrient restriction by 49.1%. Melatonin supplementation and maternal nutrient restriction did not influence (P ≥ 0.15) fetal small intestinal protein concentration, or glucoamylase, isomaltase, and lactase activity. Maternal nutrient restriction from mid-to-late gestation decreased (P = 0.05) fetal maltase activity per gram intestine by 20.5% but did not influence fetal maltase activity per gram protein. These data indicate that some maternal and fetal carbohydrases are influenced by nutrient restriction and melatonin supplementation in sheep. More information is needed to understand how nutritional and hormonal factors regulate digestive enzyme activity in ruminants to design improved maternal nutrition programs to optimize fetal growth and development while maintaining maternal productivity.

Entanglement Swapping with Photons Generated on Demand by a Quantum Dot.

Photonic entanglement swapping, the procedure of entangling photons without any direct interaction, is a fundamental test of quantum mechanics and an essential resource to the realization of quantum networks. Probabilistic sources of nonclassical light were used for seminal demonstration of entanglement swapping, but applications in quantum technologies demand push-button operation requiring single quantum emitters. This, however, turned out to be an extraordinary challenge due to the stringent prerequisites on the efficiency and purity of the generation of entangled states. Here we show a proof-of-concept demonstration of all-photonic entanglement swapping with pairs of polarization-entangled photons generated on demand by a GaAs quantum dot without spectral and temporal filtering. Moreover, we develop a theoretical model that quantitatively reproduces the experimental data and provides insights on the critical figures of merit for the performance of the swapping operation. Our theoretical analysis also indicates how to improve state-of-the-art entangled-photon sources to meet the requirements needed for implementation of quantum dots in long-distance quantum communication protocols.

BAYESIAN ANALYSIS OF COSMIC RAY PROPAGATION: EVIDENCE AGAINST HOMOGENEOUS DIFFUSION.

We present the results of the most complete scan of the parameter space for cosmic ray (CR) injection and propagation. We perform a Bayesian search of the main GALPROP parameters, using the MultiNest nested sampling algorithm, augmented by the BAMBI neural network machine-learning package. This is the first study to separate out low-mass isotopes (p, p ¯ , and He) from the usual light elements (Be, B, C, N, and O). We find that the propagation parameters that best-fit p, p ¯ , and He data are significantly different from those that fit light elements, including the B/C and 10Be/9Be secondary-to-primary ratios normally used to calibrate propagation parameters. This suggests that each set of species is probing a very different interstellar medium, and that the standard approach of calibrating propagation parameters using B/C can lead to incorrect results. We present posterior distributions and best-fit parameters for propagation of both sets of nuclei, as well as for the injection abundances of elements from H to Si. The input GALDEF files with these new parameters will be included in an upcoming public GALPROP update.

Universal recovery of the energy-level degeneracy of bright excitons in InGaAs quantum dots without a structure symmetry.

The lack of structural symmetry which usually characterizes semiconductor quantum dots lifts the energetic degeneracy of the bright excitonic states and hampers severely their use as high-fidelity sources of entangled photons. We demonstrate experimentally and theoretically that it is always possible to restore the excitonic degeneracy by the simultaneous application of large strain and electric fields. This is achieved by using one external perturbation to align the polarization of the exciton emission along the axis of the second perturbation, which then erases completely the energy splitting of the states. This result, which holds for any quantum dot structure, highlights the potential of combining complementary external fields to create artificial atoms meeting the stringent requirements posed by scalable semiconductor-based quantum technology.

Nanomembrane quantum-light-emitting diodes integrated onto piezoelectric actuators.

We integrate resonant-cavity light-emitting diodes containing quantum dots onto substrates with giant piezoelectric response. Via strain, the energy of the photons emitted by the diode can be precisely controlled during electrical injection over a spectral range larger than 20 meV. Simultaneously, the exciton fine-structure-splitting and the biexciton binding energy can be tuned to the values required for entangled photon generation.

Electron mass in dilute nitrides and its anomalous dependence on hydrostatic pressure.

The dependence of the electron mass on hydrostatic pressure P in N-diluted GaAs1-xNx (x=0.10% and 0.21%) is investigated by magnetophotoluminescence. Exceedingly large fluctuations (up to 60%/kbar) in the electron mass with increasing P are found. These originate from a pressure-driven tuning of the hybridization degree between the conduction band minimum and specific nitrogen-related states. Present results suggest a hierarchy between different nitrogen complexes as regards the extent of the perturbation these complexes exert on the electronic properties of the GaAs host.

Increased intima-media thickness of the carotid artery wall, normal blood pressure profile and normal left ventricular mass in subjects with primary hyperparathyroidism.

OBJECTIVE: Despite the increasing evidence that primary hyperparathyroidism (PHPT) contributes to greater risk of cardiovascular morbidity and mortality, its exact role in the development of cardiovascular changes and its clinical significance are still controversial. Given the multiple influence of PHPT on the cardiovascular system, this study aimed to assess the effects of PHPT on blood pressure profile, and on features of the heart and arterial vessels in normotensive symptomless patients. DESIGN: Twenty patients (8 males and 12 females) with a median age of 51.5 years (range 44 to 65 years) were evaluated and the results were compared with those of 20 controls matched for age, gender and body mass index. Patients' parathyroid hormone levels ranged from 172 to 454 pg/ml and Ca levels ranged from 11.4 to 13.5 mg/dl. Fasting levels of glucose, insulin, total and high density lipoprotein cholesterol and triglycerides were within the normal range in all subjects recruited. METHODS: Twenty-four-hour blood pressure profile, left ventricle (LV) dimension and carotid artery anatomy were investigated, the latter two by ultrasonography. RESULTS: No difference was found between the patients and controls in blood pressure profile, when the following parameters were considered: supine systolic/diastolic pressure, average 24-h systolic, diastolic and mean arterial pressure, day-time mean arterial pressure and fall in nocturnal blood pressure (-17% and -18% respectively). Heart rate and all parameters of LV mass were similar in patients and controls. The only alteration found in patients was in significantly greater carotid intimal-medial thickness (IMT) (P<0.001). Atherosclerotic plaques were more frequent in patients than in controls, with a difference reaching a trend (40% vs 10%, chi(2)=4.8; P=0.091). Considering that the carotid IMT is considered to be a marker of systemic atherosclerosis, our finding suggests early atherosclerotic changes in PHPT. No correlation was found between the severity and cardiovascular manifestation of PHPT. CONCLUSIONS: Vascular changes may occur due to a combination of structural and functional impairments in PHPT patients, likely as a result of altered calcium metabolism and impaired equilibrium of other factors regulating vascular function. Both extent and duration of PHPT can play a relative role in the development of cardiovascular complications. Considering that PHPT is now recognized as a quite common and often symptomless endocrine disorder, the evidence of cardiovascular manifestation in normotensive patients, found by this morphological study, suggests a possible implication for the management of such patients. In this light, screening for abnormalities in cardiovascular system function should be recommended in all PHPT subjects.

Cosmic microwave background anisotropies with mixed isocurvature perturbations.

In the light of the recent high quality data of the cosmic microwave background anisotropies, several estimations of cosmological parameters have been published. We study to what extent these estimations depend on assumptions about the initial conditions of the cosmological perturbations, which are usually supposed to be adiabatic. We show that, for more generic initial conditions, not only the best fit values are very different but the allowed parameter range enlarges dramatically. This raises the question which cosmological information (matter content of the Universe vs physics of inflation) can be reliably extracted from these data.

[Evaluation of oocyte maturity in patients undergoing ICSI and R-FSH treatment]. / La valutazione della maturazione ovacitaria in pazienti sottoposte ad ICSI e trattate con R-FSH.

BACKGROUND: This study compares embryo quality, fertilisation rate and pregnancy rates after ICSI related with the quality of oocytes achieved after r-FSH stimulation. METHODS: We evaluated 955 oocytes from patients following r-FSH and 643 oocytes from patients stimulated with ultrapure urinary FSH. The oocytes were divided into: a) normal oocytes; b) ooctyes with extra cytoplasmatic abnormalities (dark zona pellucida, wide perivitelline space); c) oocytes with cytoplasmatic abnormalities (dark cytoplasm, granular cytoplasm, retractile body), d) oocytes with shape abnormalities; e) oocytes with double abnormalities; f) oocytes with triple abnormalities. The embryos were divided into: A) even and homogeneous blastomeres without fragmentation; B) even and homogeneous blastomeres with <20% fragmentation; C) uneven and non-homogeneous blastomeres with 20-50% fragmentation; D) uneven and non homogeneous blastomere with >50% fragmentation. RESULTS: 40.9% of oocytes from patients treated with r-FSH have a normal morphology vs 35.2% of control groups (p<0.04). Abnormalities have a similar frequency in the two groups, except for the presence of three combined abnormalities (7.7 vs 5.4%; p<0.04). Fertilisation rate, cleavage rate, oocyte quality and pregnancy rate do not appear to be influenced by oocyte morphology and the type of FSH used for stimulation. CONCLUSIONS: The administration of r-FSH allows a large number of oocytes to be rescued, with a high incidence of normal morphology. The fertilisation rate and the quality of embryos obtained from oocytes with structural abnormalities are similar to those observed in morphologically normal oocytes. Even the probability of pregnancy is similar in the two groups.

B-Myb overexpression results in activation and increased Fas/Fas ligand-mediated cytotoxicity of T and NK cells.

The human B-myb gene encodes a transcriptional regulator that plays an important role in cell cycle progression, differentiation, and survival. To assess the in vivo role of B-myb, we investigated the phenotype of mouse transgenic lines in which B-Myb expression in lymphoid tissues was driven by the LCK proximal promoter. Overexpression of B-Myb had no measurable effect on the subsets of splenic and thymic lymphocytes, but was associated with increased expression of Fas ligand in NK and T cells. B-Myb-overexpressing splenocytes expressed higher IFN-gamma levels and contained higher percentages of cytokine-producing cells than wild-type (wt) splenocytes, as detected by Western blot analysis and ELISPOT assays, respectively. Ex vivo-cultured transgenic thymocytes and splenocytes had decreased survival compared with the corresponding cells from wt mice, possibly dependent on increased expression of Fas ligand. In addition, Fas ligand-dependent cytotoxicity of transgenic T and NK cells was significantly higher than that mediated by their wt counterparts. Together, these results indicate that B-Myb overexpression results in T and NK cell activation and increased cytotoxicity. Therefore, in addition to its well-established role in proliferation and differentiation, B-myb also appears to be involved in activation of NK and T cells and in their regulation of Fas/Fas ligand-mediated cytotoxicity

Bcl-2 expression restores the leukemogenic potential of a BCR/ABL mutant defective in transformation.

Growth factor-dependent hematopoietic cell lines expressing the BCR/ABL oncoprotein of the Ph chromosome show growth factor-independent proliferation and resistance to apoptosis. Apoptosis resistance of BCR/ABL-expressing cells may depend on enhanced expression of anti-apoptotic proteins as well as reduced expression and/or inactivation of pro-apoptotic proteins. Compared to myeloid precursor 32Dcl3 cells expressing wild type BCR/ABL, cells expressing a BCR/ABL mutant lacking amino acids 176-426 in the BCR domain (p185 delta BCR) are susceptible to apoptosis induced by interleukin-3 (IL-3) deprivation. These cells exhibited the hypophosphorylated apoptotic BAD and markedly reduced levels of Bcl-2. Upon ectopic expression of Bcl-2, these cells showed no changes in BAD phosphorylation, but they became apoptosis-resistant and proliferated in the absence of IL-3, albeit more slowly than cells expressing wild type BCR/ABL. Moreover, the p185 delta BCR/Bcl-2 double transfectants were leukemogenic when injected into immunodeficient mice, but Bcl-2 expression did not restore the leukemia-inducing effects of p185 delta BCR to the levels of wild type BCR/ABL. Leukemic cells recovered from the spleen of mice injected with p185 delta BCR/Bcl-2 cells did not show rearrangements in the Bcl-2 genomic locus, but they exhibited enhanced proliferation in culture and induced a rapidly fatal disease process when inoculated in secondary recipient mice. Together, these data support the importance of anti-apoptotic pathways for BCR/ABL-dependent leukemogenesis and suggest that Bcl-2 expression promotes secondary changes leading to a more aggressive tumor phenotype. (Blood. 2000;96:3915-3921)

Differential role of p38 and c-Jun N-terminal kinase 1 mitogen-activated protein kinases in NK cell cytotoxicity.

The serine-threonine mitogen-activated protein kinase (MAPK) family includes extracellular signal-regulated kinases (ERK), c-Jun N-terminal kinases (JNK), and p38 kinases. In NK cells, spontaneous or Ab-mediated recognition of target cells leads to activation of an ERK-2 MAPK-dependent biochemical pathway(s) involved in the regulation of NK cell effector functions. Here we assessed the roles of p38 and JNK MAPK in NK cell-mediated cytotoxicity. Our data indicate that p38 is activated in primary human NK cells upon stimulation with immune complexes and interaction with NK-sensitive target cells. FcgammaRIIIA-induced granule exocytosis and both spontaneous and Ab-dependent cytotoxicity were reduced in a dose-dependent manner in cells pretreated with either of two specific inhibitors of this kinase. Target cell-induced IFN-gamma and FcgammaRIIIA-induced TNF-alpha mRNA accumulation was similarly affected under the same conditions. Lack of inhibition of NK cell cytotoxicity in cells overexpressing an inactive form of JNK1 indicates that this kinase, activated only upon FcgammaRIIIA ligation, does not play a significant role in cytotoxicity. These data underscore the involvement of p38, but not JNK1, in the molecular mechanisms regulating NK cell cytotoxicity.

Activation of mitochondrial Raf-1 is involved in the antiapoptotic effects of Akt.

The Akt serine/threonine kinase is required for the survival of many cell types and for transformation of hematopoietic cells by the BCR/ABL oncogenic tyrosine kinase. Analysis of the potential mechanisms whereby Akt promotes survival of hematopoietic cells revealed that it induced the activity of plasma membrane and mitochondrial Raf-1 in a Ras-independent, but PKC-dependent manner. Inhibition of plasma membrane Raf-1-dependent mitogen-activated protein kinase activity had no effect on the enhanced survival of cells expressing Akt. By contrast, suppression of mitochondrial Raf-1 enzymatic activity by expression of a mitochondria-targeted Raf-1 dominant-negative mutant rendered Akt-expressing cells susceptible to apoptosis induced by growth factor deprivation and was accompanied by inhibition of BAD, but not mitogen-activated protein kinase, phosphorylation. Together, these data indicate that PKC-dependent activation of Raf-1 plays an important role in Akt-dependent antiapoptotic effects.

D-dimer assay predicts mortality in critically ill patients without disseminated intravascular coagulation or venous thromboembolic disease.

OBJECTIVE: To determine if D-dimer predicts outcomes in critically ill patients. DESIGN: Observational, cohort study. SETTING: Medical intensive care unit (MICU) of a tertiary care hospital. PATIENTS AND PARTICIPANTS: Seventy-four patients consecutively admitted to the MICU. INTERVENTIONS: D-dimer was measured by latex agglutination within 12 h of admission to the MICU. MEASUREMENTS AND RESULTS: Of the study population, 43.2% had positive D-dimers. The in-hospital mortality rate in D-dimer positive patients was 28.1% as compared to 7.1% in D-dimer negative subjects (p = 0.024). D-dimer positive patients had significantly greater frequencies of venous thromboses (21.9% vs 4.8%, p = 0.035). CONCLUSIONS: The D-dimer assay identifies patients at increased risk for mortality and may be a more sensitive test to determine the presence of underlying microvascular pathology in critically ill patients. A positive D-dimer at admission to the MICU is associated with an increased risk for the later development of a venous thromboembolic event (VTE).

Dependence of both spontaneous and antibody-dependent, granule exocytosis-mediated NK cell cytotoxicity on extracellular signal-regulated kinases.

Extracellular signal-regulated kinases (ERK, also known as mitogen-activated protein kinases) are serine-threonine kinases transducing signals elicited upon ligand binding to several tyrosine kinase-associated receptors. We have reported that ERK2 phosphorylation and activation follows engagement of the low affinity receptor for the Fc portion of IgG (CD16) on NK cells, and is necessary for CD16-induced TNF-alpha mRNA expression. Here, we analyzed the involvement of ERK in NK cell-mediated cytotoxicity and IFN-gamma expression induced upon stimulation with targets cells, coated or not with Abs. Our data indicate that, as with immune complexes, ERK2 phosphorylation occurs in human primary NK cells upon interaction with target cells sensitive to granule exocytosis-mediated spontaneous cytotoxicity, and that this regulates both target cell- and immune complex-induced cytotoxicity and IFN-gamma mRNA expression. A specific inhibitor of mitogen-activated protein kinase kinase reduced both spontaneous and Ab-dependent cytotoxicity in a dose-dependent manner involving, at least in part, inhibition of granule exocytosis without affecting effector/target cell interaction and rearrangement of the cytoskeleton proteins actin and tubulin. Involvement of ERK in the regulation of Ca2+-dependent cell-mediated cytotoxicity was confirmed, using a genetic approach, in primary NK cells infected with a recombinant vaccinia virus encoding an ERK inactive mutant. These data indicate that the biochemical pathways elicited in NK cells upon engagement of receptors responsible for either spontaneous or Ab-dependent recognition of target cells, although distinct, utilize ERK as one of their downstream molecules to regulate effector functions.

TLS/FUS, a pro-oncogene involved in multiple chromosomal translocations, is a novel regulator of BCR/ABL-mediated leukemogenesis.

The leukemogenic potential of BCR/ABL oncoproteins depends on their tyrosine kinase activity and involves the activation of several downstream effectors, some of which are essential for cell transformation. Using electrophoretic mobility shift assays and Southwestern blot analyses with a double-stranded oligonucleotide containing a zinc finger consensus sequence, we identified a 68 kDa DNA-binding protein specifically induced by BCR/ABL. The peptide sequence of the affinity-purified protein was identical to that of the RNA-binding protein FUS (also called TLS). Binding activity of FUS required a functional BCR/ABL tyrosine kinase necessary to induce PKCbetaII-dependent FUS phosphorylation. Moreover, suppression of PKCbetaII activity in BCR/ABL-expressing cells by treatment with the PKCbetaII inhibitor CGP53353, or by expression of a dominant-negative PKCbetaII, markedly impaired the ability of FUS to bind DNA. Suppression of FUS expression in myeloid precursor 32Dcl3 cells transfected with a FUS antisense construct was associated with upregulation of the granulocyte-colony stimulating factor receptor (G-CSFR) and downregulation of interleukin-3 receptor (IL-3R) beta-chain expression, and accelerated G-CSF-stimulated differentiation. Downregulation of FUS expression in BCR/ABL-expressing 32Dcl3 cells was associated with suppression of growth factor-independent colony formation, restoration of G-CSF-induced granulocytic differentiation and reduced tumorigenic potential in vivo. Together, these results suggest that FUS might function as a regulator of BCR/ABL leukemogenesis, promoting growth factor independence and preventing differentiation via modulation of cytokine receptor expression.

T wave alternans associated with HIV cardiomyopathy, erythromycin therapy, and electrolyte disturbances.

We report a case of T wave alternans in a patient with HIV cardiomyopathy. T wave alternans is an unusual electrocardiographic finding in acquired long QT syndromes that can precede the development of torsades de pointes. Our patient had multiple risk factors for the development of the acquired long QT syndrome, including HIV cardiomyopathy, electrolyte disturbances, and erythromycin therapy. T wave alternans has not been described previously with HIV cardiomyopathy and only rarely with erythromycin therapy. Patients who have HIV cardiomyopathy and who receive intravenous erythromycin may benefit from monitoring for QT prolongation and electrolyte disturbances to avoid the development of torsades de pointes.

The SH3 domain contributes to BCR/ABL-dependent leukemogenesis in vivo: role in adhesion, invasion, and homing.

To determine the possible role of the BCR/ABL oncoprotein SH3 domain in BCR/ABL-dependent leukemogenesis, we studied the biologic properties of a BCR/ABL SH3 deletion mutant (delta SH3 BCR/ABL) constitutively expressed in murine hematopoietic cells. delta SH3 BCR/ABL was able to activate known BCR/ABL-dependent downstream effector molecules such as RAS, PI-3kinase, MAPK, JNK, MYC, JUN, STATs, and BCL-2. Moreover, expression of delta SH3 BCR/ABL protected 32Dcl3 murine myeloid precursor cells from apoptosis, induced their growth factor-independent proliferation, and resulted in transformation of primary bone marrow cells in vitro. Unexpectedly, leukemic growth from cells expressing delta SH3 BCR/ABL was significantly retarded in SCID mice compared with that of cells expressing the wild-type protein. In vitro and in vivo studies to determine the adhesive and invasive properties of delta SH3 BCR/ABL-expressing cells showed their decreased interaction to collagen IV- and laminin-coated plates and their reduced capacity to invade the stroma and to seed the bone marrow and spleen. The decreased interaction with collagen type IV and laminin was consistent with a reduced expression of alpha 2 integrin by delta SH3 BCR/ABL-transfected 32Dcl3 cells. Moreover, as compared with wild-type BCR/ABL, which localizes primarily in the cytoskeletal/membrane fraction, delta SH3 BCR/ABL was more evenly distributed between the cytoskeleton/membrane and the cytosol compartments. Together, the data indicate that the SH3 domain of BCR/ABL is dispensable for in vitro transformation of hematopoietic cells but is essential for full leukemogenic potential in vivo.