Phase-locking of octave-spanning optical frequency comb based on Kerr-lens mode-locked Yb:KYW laser to reference laser

We phase locked an octave-spanning optical frequency comb based on a laser-diode-pumped Kerr-lens mode-locked Yb:KYW laser to a reference laser. We controlled the cavity length of the mode-locked laser to phase lock the mode frequency of the comb to the reference laser. This was conducted using a fast piezoelectric-actuated mirror on a lead-filled mount, which was aimed at damping the mechanical resonances. We achieved a servo bandwidth of 200 kHz, a residual phase noise of 0.47 rad, and a power concentration to a carrier of 91%. To extend the locking duration of the carrier-envelope offset frequency, we compensated its slow drift using the position of the Yb:KYW crystal while the pump-laser power was controlled to achieve its phase locking. We continuously maintained the full phase locking of the comb for 3 h until the reference lasers were out of lock

Impact of debt financing on financial performance of small and medium Enterprises in Kisii Central Sub-County

The choice of financial structure and financial management has a greater effect on the financial performance of most firms in the world and in particular Kenya. While most firms try to find a solution to balancing both, financial structure choice and its impact on financial performance remains a greater dilemma to all small and medium enterprises in Kisii County. This was a descriptive survey and questionnaires were used in collecting data from the respondents. Random sampling was used as the general sampling technique with the aid of the Yamane’s formula to select 109 SMEs to participate in the study from a target population of 150 SMEs in Kisii Central Sub-County. Statistical package for social sciences (SPSS version 23) was used to analyze both qualitative and quantitative data that was collected during the study. The owner controls the business and enjoys profits whenever it’s high and bears the risk alone. It does not entail any charge. This therefore shows equity capital forms higher proportion of financial structure hence has a significant effect on financial performance of SMEs. From the study retaining earnings was well appreciated irrespective of not having a significant effect on financial performance due to challenges of raising it. It stands a chance of being the best source of finance for expansion because it is the cheapest and painless method of raising additional capital. Management of SMEs should ensure that the financial structure of the firm is always at optimum. The firm cannot only survive on equity capital due to its low risk, also cannot wholly depend on debts due to high risk, more so retained earnings is only realized after making profi

Understanding the role of the perivascular space in cerebral small vessel disease

Small vessel diseases are a group of disorders that result from pathological alteration of the small blood vessels in the brain, including the small arteries, capillaries and veins. Of the 35-36 million people that are estimated to suffer from dementia worldwide, up to 65% have an SVD component. Furthermore, SVD causes 20-25% of strokes, worsens outcome after stroke and is a leading cause of disability, cognitive impairment and poor mobility. Yet the underlying cause(s) of SVD are not fully understood.Magnetic resonance imaging (MRI) has confirmed enlarged perivascular spaces (PVS) as a hallmark feature of SVD. In healthy tissue, these spaces are proposed to form part of a complex brain fluid drainage system which supports interstitial fluid exchange and may also facilitate clearance of waste products from the brain. The pathophysiological signature of PVS, and what this infers about their function and interaction with cerebral microcirculation, plus subsequent downstream effects on lesion development in the brain has not been established. Here we discuss the potential of enlarged PVS to be a unique biomarker for SVD and related brain disorders with a vascular component. We propose that widening of PVS suggests presence of peri-vascular cell debris and other waste products that forms part of a vicious cycle involving impaired cerebrovascular reactivity (CVR), blood-brain barrier (BBB) dysfunction, perivascular inflammation and ultimately impaired clearance of waste proteins from the interstitial fluid (ISF) space, leading to accumulation of toxins, hypoxia and tissue damage.Here, we outline current knowledge, questions and hypotheses regarding understanding the brain fluid dynamics underpinning dementia and stroke through the common denominator of SVD

Efficacy of T2*-Weighted Gradient-Echo MRI in Early Diagnosis of Cerebral Venous Thrombosis with Unilateral Thalamic Lesion

Cerebral venous thrombosis (CVT) is an uncommon cause of stroke with diverse etiologies and varied clinical presentations. Because of variability in clinical presentation and neuroimaging, CVT remains a diagnostic challenge. Recently, some studies have highlighted the value of T2*-weighted gradient-echo MRI (T2*WI) in the diagnosis of CVT. We report the case of a 79-year-old woman with CVT due to a hypercoagulable state associated with cancer. On the initial T2-weighted image (T2WI), there was a diffuse high-intensity lesion in the right thalamus, extending into the posterior limb of the internal capsule and midbrain. T2*WI showed diminished signal and enlargement of the right basilar vein and the vein of Galen. Even though there is a wide range of differential diagnoses in unilateral thalamic lesions, and a single thalamus lesion is a rare entity of CVT, based on T2*WI findings we could make an early diagnosis and perform treatment. Our case report suggests that T2*WI could detect thrombosed veins and be a useful method of early diagnosis in CVT

Phase-locking of octave-spanning optical frequency comb based on Kerr-lens mode-locked Yb:KYW laser to reference laser

Abstract We phase locked an octave-spanning optical frequency comb based on a laser-diode-pumped Kerr-lens mode-locked Yb:KYW laser to a reference laser. We controlled the cavity length of the mode-locked laser to phase lock the mode frequency of the comb to the reference laser. This was conducted using a fast piezoelectric-actuated mirror on a lead-filled mount, which was aimed at damping the mechanical resonances. We achieved a servo bandwidth of 200 kHz, a residual phase noise of 0.47 rad, and a power concentration to a carrier of 91%. To extend the locking duration of the carrier-envelope offset frequency, we compensated its slow drift using the position of the Yb:KYW crystal while the pump-laser power was controlled to achieve its phase locking. We continuously maintained the full phase locking of the comb for 3 h until the reference lasers were out of lock.</jats:p

A contribution to the study of jewellery in early iron age Crete: the jewellery from the necropolis of Orthi Petra in Eleutherna

The dissertation examines the gold and silver jewellery from the necropolis of Orthi Petra in Eleutherna dating in the Early Iron Age (11th-7th century BC). The study also includes the gold and silver known jewellery from Crete which are systematically co-examined. The first chapter includes a detailed catalogue of the material under examination. The second chapter discusses the types and the typological issues of jewellery and includes a brief description and reference of their parallels in jewellery or in jewellery representations and their decorative subjects and motifs, which provide further information about the origin, the influences, the dating and the use of jewellery. The third chapter presents the techniques of jewellery from the necropolis of Orthi Petra, as they provide additional information about the workshop centers as well as the Cretan jewellery and its evolution. In the fourth chapter are investigated the jewellery’s iconographic subjects, the issues of iconographic subjects’ interpretation and symbolism, as well as the use of jewerelly as burial gifts or religious symbols. In the conclusions a review of the study of gold and silver jewellery from the necropolis of Orthi Petra is given and a briefly overview of the Cretan jewellery during the Early Iron Age, as well as a comparative study between them. The gold and silver jewellery from Orthi Petra’s necropolis constitute an important assemblage, the most populous of known jewellery from Crete during the Early Iron Age. They are characterized by their excellent techniques and decoration, variety, rarity and uniqueness of their types and their iconographic subjects, as well as the coexistence of Greek/Cretan-Mycenaean, Cypriot and Eastern elements of the Early Iron Age and the Bronze Age. The existence of a specific style, among others, leads to the conclusion that jewellery would have been local workshop products. The jewellery from the necropolis of Orthi Petra in Eleutherna present new data, changing the image of Cretan jewellery, give answers to issues which have concern the research, whereas others question well-established views, but clearly confirm the high level of jewellery in Crete during the Early Iron Age.Η διατριβή εξετάζει το σύνολο των χρυσών και αργυρών κοσμημάτων από τη νεκρόπολη της Ορθής Πέτρας στην Ελεύθερνα, που χρονολογούνται στην Πρώιμη Εποχή του Σιδήρου (11ος-7ος αι. π.Χ.). Η μελέτη συμπεριλαμβάνει, επίσης, το σύνολο των χρυσών και αργυρών κοσμημάτων της Κρήτης, τα οποία συνεξετάζονται συστηματικά. Στο πρώτο κεφάλαιο γίνεται αναλυτική περιγραφή, ανά είδος, των υπό μελέτη κοσμημάτων από τη νεκρόπολη της Ορθής Πέτρας. Το δεύτερο κεφάλαιο αφορά στα είδη καθώς και σε τυπολογικά ζητήματα των κοσμημάτων και περιλαμβάνει σύντομη περιγραφή και αναφορά παράλληλων παραδειγμάτων τους, σε κοσμήματα ή σε παραστάσεις κοσμημάτων και στα διακοσμητικά θέματα και μοτίβα τους, τα οποία δίνουν στοιχεία για την καταγωγή, τις επιρροές, τη χρονολόγηση αλλά και τη χρήση των κοσμημάτων. Αναφέρονται, επίσης, γενικά στοιχεία για το κάθε είδος κοσμήματος, τα δημοσιευμένα κοσμήματα από πολύτιμα μέταλλα από άλλες θέσεις της Κρήτης καθώς και συγκριτικά μεταξύ τους στοιχεία. Στο τρίτο κεφάλαιο εξετάζονται οι τεχνικές κατασκευής και διακόσμησης των κοσμημάτων από τη νεκρόπολη της Ορθής Πέτρας καθώς μπορούν να δώσουν επιπρόσθετες πληροφορίες για τα εργαστηριακά κέντρα καθώς και για την κρητική κοσμηματοτεχνία και την εξέλιξή της. Στο τέταρτο κεφάλαιο μελετώνται τα εικονογραφικά θέματα που φέρουν τα κοσμήματα. Ερευνώνται θέματα ερμηνείας και συμβολισμού των εικονογραφικών θεμάτων αλλά και χρήσης των κοσμημάτων ως ταφικών κτερισμάτων ή και ως κοσμημάτων θρησκευτικού συμβολισμού και χαρακτήρα. Στα συμπεράσματα γίνεται ανασκόπηση της μελέτης των χρυσών και αργυρών κοσμημάτων από τη νεκρόπολη της Ορθής Πέτρας και μία σύντομη επισκόπηση της κρητικής κοσμηματοτεχνίας της Πρώιμης Εποχής του Σιδήρου καθώς και συγκριτική συνεξέτασή τους. Τα χρυσά και αργυρά κοσμήματα από τη νεκρόπολη της Ορθής Πέτρας συγκροτούν ένα ιδιαίτερα σημαντικό σύνολο, το πολυπληθέστερο σύνολο γνωστών κοσμημάτων από την Κρήτη κατά την Πρώιμη Εποχή του Σιδήρου. Χαρακτηρίζονται από την εξαιρετική κατασκευή και διακόσμησή τους, την ποικιλία, τη σπανιότητα ή/και μοναδικότητα των τύπων και των εικονογραφικών τους θεμάτων. Σε αυτά συνυπάρχουν ελληνικά-κρητομυκηναϊκά, κυπριακά και ανατολικά στοιχεία της Πρώιμης Εποχής του Σιδήρου αλλά και της Εποχής του Χαλκού. Η ύπαρξη συγκεκριμένου τεχνοτροπικού ύφους καθώς και άλλα στοιχεία οδηγούν στο συμπέρασμα, ότι τα κοσμήματα θα ήταν προϊόντα τοπικού εργαστηρίου. Τα κοσμήματα από τη νεκρόπολη της Ορθής Πέτρας στην Ελεύθερνα παρέχουν νέα δεδομένα, αλλάζοντας την εικόνα της κρητικής κοσμηματοτεχνίας καθώς δίδουν απαντήσεις σε θέματα που έχουν απασχολήσει την έρευνα, θέτουν υπό αμφισβήτηση παγιωμένες απόψεις αλλά επιβεβαιώνουν σαφώς το υψηλό επίπεδο της κοσμηματοτεχνίας της Κρήτης κατά την Πρώιμη Εποχή του Σιδήρου