New optical timekeeper is 10 times more reliable than caesium atomic clocks

22 Oct 2019 Hamish Johnston

Reliable ticker: physicists have created an all-optical atomic timekeeper. (Courtesy: iStock/Altayb)

A new timekeeper based on trapped strontium atoms accumulates an error of just 48 ps over 34 days of operation – making it 10 times more reliable than current caesium time standards. This new record for performance has been set by physicists in the US and Germany, who used a silicon cavity and a diode laser to back-up the time signal generated by the atoms.

The current international time standard is Coordinated Universal Time (UTC), which combines the signals of hundreds of caesium atomic clocks worldwide.

ΓΕΝΙΚΗ ΒΙΟΛΟΓΙΑ - ΦΥΛΛΟ ΜΟΣΧΟΥ ΣΕ ΕΠΙΠΕΔΗ ΕΠΙΦΑΝΕΙΑ - ( Moss leaf surface view)

2HORSETAIL EQUISETUM SPORES WITH ELATERS (GENERAL BIOLOGY)

1 EQUISETUM HORSETAILS SPORES WITH ELATERS - ΣΠΟΡΟΙ ΜΕ ΕΛΑΤΗΡΙΑ ΤΟΥ EQUISETUM (ΓΕΝΙΚΗ ΒΙΟΛΟΓΙΑ)

1 EQUISETUM HORSETAILS SPORES WITH ELATERS - ΣΠΟΡΟΙ ΜΕ ΕΛΑΤΗΡΙΑ ΤΟΥ EQUISETUM (ΓΕΝΙΚΗ ΒΙΟΛΟΓΙΑ)

3D bacterial biofilms help tackle antimicrobial resistance crisis

02 Oct 2019 Tami Freeman

The anaerobic bacteria P. aeruginosa formed biofilms in thick constructs. Left: Photos of the 3D bioprinted biofilm at day 0 and matured biofilm at day 14 (scale bar: 1 cm). Right: 2D projection and 3D reconstructed confocal laser scanning microscopy images of matured biofilm (scale bar: 100 μm).

Antimicrobial resistance is an increasing problem worldwide, with the World Health Organization calling for urgent action to avoid a “post-antibiotic era” in which common infections and minor injuries can once again kill.

Bacteria in acute infections usually exist in a free-swimming state and can be treated with antimicrobials. Chronic infections, however, can lead to the development of bacterial biofilms – 3D structures of bacterial cells – which are up to 1000 times more resistant and can render standard antimicrobial therapies ineffective. Unfortunately, most methods used to study biofilm resistance are 2D in nature, and thus unable to reflect complex 3D infection processes seen in vivo.

Non-abelian Aharonov–Bohm experiment done at long last

01 Oct 2019

Phase shift: Images showing interference patterns (top) and a “Wilson loop” (bottom) were produced by the researchers to confirm the presence of non-Abelian gauge fields. (Courtesy: MIT)

For the first time, physicists in the US have confirmed a decades-old theory regarding the breaking of time-reversal symmetry in gauge fields. Marin Soljacic at the Massachusetts Institute of Technology and an international team of researchers have made this first demonstration of the “non-Abelian Aharonov–Bohm effect” in two optics experiments. With improvements, their techniques could find use in optoelectronics and fault-tolerant quantum computers.

First emerging in Maxwell’s famous equations for classical electrodynamics, a gauge theory is a description of the physics of fields. Gauge theories have since become an important part of physicists’ descriptions of the dynamics of elementary particles – notably the theory of quantum electrodynamics.

Optical imaging monitors brain blood flow in children with sickle cell disease

01 Oct 2019

The Buckley lab researchers (from left to right): Eashani Sathialingam, Rowan Brothers, Paul (Seung Yup) Lee, Erin Buckley, Hongting Zhao and Kyle Cowdrick. (Courtesy: Erin Buckley)

A team of US-based researchers has demonstrated how low-cost, non-invasive diffuse correlation spectroscopy (DCS) can improve the assessment of cerebral blood flow in children with sickle cell disease – a genetic blood disorder that can have a substantial impact upon the brain.

DCS is an optical technique that employs near-infrared light to relate intensity fluctuations of multiply scattered reflected light detected at the tissue surface to a blood flow index (BFI) in the underlying tissue. The researchers, based at the Georgia Institute of Technology, Emory University and Children’s Healthcare of Atlanta, used DCS to quantify brain blood flow in 11 children with sickle cell disease along with 11 healthy controls. As expected, they found that BFI was significantly higher in subjects with sickle cell disease than in the control group (Neurophotonics 10.1117/1.NPh.6.3.035006).

“Previous studies using other neuroimaging modalities have shown that kids with sickle cell disease have elevated blood flow in their brain as a compensatory mechanism to improve oxygen delivery in the face of chronic anaemia,” says co-author Erin Buckley from Georgia Tech and Emory University School of Medicine.

Horsetail Equisetum spores with elaters. (Σπόρος με ελατήρια του Equisetum)

Horsetail Equisetum spores with elaters. (Σπόρος με ελατήρια του Equisetum) 
(ΓΕΝΙΚΗ ΒΙΟΛΟΓΙΑ)

Τα φυτά Equisetum (αλογοουρά) αναπαράγονται παράγοντας μικροσκοπικά σφαιρικά σπόρια που έχουν τυπικά διάμετρο 50 μικρομέτρων. Τα σπόρια έχουν τέσσερα ελάσματα, τα οποία είναι εύκαμπτα δερμάτινα εξαρτήματα που αρχικά τυλίγονται γύρω από το κύριο σώμα των σπορίων και τα οποία αναπτύσσονται κατά την ξήρανση ή την αναδίπλωση πίσω στον υγρό αέρα. Εάν πιστεύεται ότι οι εκτοξευτήρες βοηθούν στη διασπορά, ο ακριβής μηχανισμός για την κίνηση των σπορίων παραμένει ασαφής στη βιβλιογραφία. Σε αυτό το χειρόγραφο παρουσιάζουμε παρατηρήσεις των «περιπάτων» και των «πηδημάτων» των σπόρων Equisetum, που είναι νέοι τύποι μηχανισμών μετακίνησης των σπορίων σε σύγκριση με τους άλλους σπόρους. Οι βόλτες οδηγούνται από κύκλους υγρασίας, όπου κάθε κύκλος προκαλεί ένα μικρό βήμα σε τυχαία κατεύθυνση. Το εύρος διασποράς από το περίπατο είναι περιορισμένο, αλλά ο περίπατος παρέχει τα βασικά βήματα είτε για έξοδο από το χώρο του σπόρου είτε για αναπροσανατολισμό και αναδίπλωση. Τα άλματα εμφανίζονται όταν τα σπόρια ξαφνικά πιέζουν τον εαυτό τους αφού σφίξουν καλά.

ΓΕΝΙΚΗ ΒΙΟΛΟΓΙΑ (ΚΑΡΠΟΦΟΡΟΣ ΚΟΡΜΟΣ ΜΑNΙΤΑΡΙΟΥ PSALLIOTA - FROUTING BODY OF MUSHROOM PSALLIOTA)

ΓΕΝΙΚΗ ΒΙΟΛΟΓΙΑ (ΚΑΡΠΟΦΟΡΟΣ ΚΟΡΜΟΣ ΜΑNΙΤΑΡΙΟΥ PSALLIOTA - FROUTING BODY OF MUSHROOM PSALLIOTA)