Measurements of the instantaneous velocity difference and local velocity with a fiber-optic coupler

New optical arrangements with two single-mode input fibers and a fiber-optic coupler are devised to measure the instantaneous velocity difference and local velocity. The fibers and the coupler are polarization-preserving to guarantee a high signal-to-noise ratio. When the two input fibers are used to collect the scattered light with the same momentum transfer vector but from two spatially separated regions in a flow, the obtained signals interfere when combined via the fiber-optic coupler. The resultant light received by a photomultiplier tube contains a cross-beat frequency proportional to the velocity difference between the two measuring points. If the two input fibers are used to collect the scattered light from a common scattering region but with two different momentum transfer vectors, the resultant light then contains a self-beat frequency proportional to the local velocity at the measuring point. The experiment shows that both the cross-beat and self-beat signals are large and the standard laser Doppler signal processor can be used to measure the velocity difference and local velocity in real time. The new technique will have various applications in the general area of fluid dynamics.Comment: Patent number: 67437 for associated information on the hardware, see http://karman.phyast.pitt.edu/horvath

Pipe network model for scaling of dynamic interfaces in porous media

We present a numerical study on the dynamics of imbibition fronts in porous media using a pipe network model. This model quantitatively reproduces the anomalous scaling behavior found in imbibition experiments [Phys. Rev. E {\bf 52}, 5166 (1995)]. Using simple scaling arguments, we derive a new identity among the scaling exponents in agreement with the experimental results.Comment: 13 pages, 3 figures, REVTeX, to appear in Phys. Rev. Let

Comparison of the efficacy and safety of commercially available fixed ratio combinations of insulin degludec/liraglutide (IDegLira) and insulin glargine/lixisenatide (iGlarLixi) - a network meta-analysis

AIMS: To compare the efficacy and safety of commercially available fixed ratio combinations (FRC) of glucagon-like peptide 1 receptor agonists (GLP-1RA) and basal insulins by a network meta-analysis (NMA) of randomised controlled trials (RCT) of type 2 diabetes patients. METHODS: We report a systematic review and network meta-analyses of RCTs of type 2 diabetes patients randomized to FRCs or to their components for ≥24-weeks reported in PubMed or ClinicalTrials.gov until 28/FEB/2022. Primary outcome was attained HbA1c. Secondary outcomes included fasting plasma glucose, change in body weight, and incident hypoglycaemia. Treatment effects were estimated as mean differences and standard errors (MD; [SE]) or odds ratios (OR) with 95% confidence intervals (95%CI) using iGlarLixi as reference. RESULTS: We included 29 RCTs of the 1404 papers identified. No direct comparison between FRCs were found. After excluding some insulin capped trials to reach model consistency, both FRCs were more efficacious regarding HbA1c than their components, however no difference between FRCs were found (MD: -0.10 [SE: 0.10]%). The effect of IDegLira (-0.47 [0.24] mmol/l) and basal insulins was similar to that of iGlarLixi (ref.) on fasting glucose, while GLP-1RA had lower efficacy than iGlarLixi. Weight gain was lower with GLP-1RAs and IDegLira (-0.72 [0.32] kg) than iGlarLixi (ref.) and higher with basal insulins. Incident hypoglycemia (based on different definitions) was least frequent with GLP-1RAs followed by IDegLira (OR 0.78 95%CI 0.39-1.57), iGlarLixi (ref.) and basal insulins. CONCLUSIONS: Regarding HbA1c, both FRCs were more efficacious over their individual components with similar efficacies of the two FRCs

Anomalous density dependence of static friction in sand

We measured experimentally the static friction force $F_s$ on the surface of a glass rod immersed in dry sand. We observed that $F_s$ is extremely sensitive to the closeness of packing of grains. A linear increase of the grain-density yields to an exponentially increasing friction force. We also report on a novel periodicity of $F_s$ during gradual pulling out of the rod. Our observations demonstrate the central role of grain bridges and arches in the macroscopic properties of granular packings.Comment: plain tex, 6 pages, to appear in Phys.Rev.

Trend of pregnancy outcomes in type 1 diabetes compared to control women: a register-based analysis in 1996-2018

INTRODUCTION: In 1989, the St Vincent declaration aimed to approximate pregnancy outcomes of diabetes to that of healthy pregnancies. We aimed to compare frequency and trends of outcomes of pregnancies affected by type 1 diabetes and controls in 1996-2018. METHODS: We used anonymized records of a mandatory nation-wide registry of all deliveries between gestational weeks 24 and 42 in Hungary. We included all singleton births (4,091 type 1 diabetes, 1,879,183 controls) between 1996 and 2018. We compared frequency and trends of pregnancy outcomes between type 1 diabetes and control pregnancies using hierarchical Poisson regression. RESULTS: The frequency of stillbirth, perinatal mortality, large for gestational age, caesarean section, admission to neonatal intensive care unit (NICU), and low Appearance, Pulse, Grimace, Activity, and Respiration (APGAR) score was 2-4 times higher in type 1 diabetes compared to controls, while the risk of congenital malformations was increased by 51% and SGA was decreased by 42% (all p<0.05). These observations remained significant after adjustment for confounders except for low APGAR scores. We found decreasing rate ratios comparing cases and controls over time for caesarean sections, low APGAR scores (p<0.05), and for NICU admissions (p=0.052) in adjusted models. The difference between cases and controls became non-significant after 2009. No linear trends were observed for the other outcomes. CONCLUSIONS: Although we found that the rates of SGA, NICU care, and low APGAR score improved in pregnancies complicated by type 1 diabetes, the target of the St Vincent Declaration was only achieved for the occurrence of low APGAR scores

The clustering of gamma-ray bursts in the Hercules–Corona Borealis Great Wall: the largest structure in the Universe?

The Hercules–Corona Borealis Great Wall is a statistically significant clustering of gamma-ray bursts (GRBs) around redshift 2. Motivated by recent theoretical results indicating that a maximal Universal structure size may indeed coincide with its estimated size (2–3 Gpc), we reexamine the question of this Great Wall’s existence from both observational and theoretical perspectives. Our statistical analyses confirm the clustering’s presence in the most reliable data set currently available, and we present a video showing what this data set looks like in 3D. Cosmological explanations (i.e. having to do with the distribution of gravitating matter) and astrophysical explanations (i.e. having to do with the rate of star formation over cosmic time and space) regarding the origin of such a structure are presented and briefly discussed and the role of observational bias is also discussed at length. This, together with the scientific importance of using GRBs as unique cosmological probes, emphasises the need for future missions such as the THESEUS satellite, which will provide us with unprecedentedly homogeneous data of GRBs with measured redshifts. We conclude from all this that the Hercules–Corona Borealis Great Wall may indeed be the largest structure in the Universe – but to be able to decide conclusively whether it actually exists, we need THESEUS

Exploration of the high-redshift universe enabled by THESEUS

At peak, long-duration gamma-ray bursts are the most luminous sources of electromagnetic radiation known. Since their progenitors are massive stars, they provide a tracer of star formation and star-forming galaxies over the whole of cosmic history. Their bright power-law afterglows provide ideal backlights for absorption studies of the interstellar and intergalactic medium back to the reionization era. The proposed THESEUS mission is designed to detect large samples of GRBs at z > 6 in the 2030s, at a time when supporting observations with major next generation facilities will be possible, thus enabling a range of transformative science. THESEUS will allow us to explore the faint end of the luminosity function of galaxies and the star formation rate density to high redshifts; constrain the progress of re-ionisation beyond z greater than or similar to 6; study in detail early chemical enrichment from stellar explosions, including signatures of Population III stars; and potentially characterize the dark energy equation of state at the highest redshifts