MUSCLE ACTIVITY OF THE TRUNK AND UPPER LIMBS IN RACE WALKING

Race walking requires high technical mastery of competitors based on biomechanical laws. These, in turn, are the basis of high sports results and effective techniques. Research in this direction mainly focuses on the work of the lower extremities. From this point of view, this study aims to determine the muscle activity of selected muscles on the upper body during race walking. The method of study is surface electromyography of the following muscles: m. Erector spinae longissimus; m. Rectus abdominis; m. Obliquus externus abdominis; m. Musculus trapezius (middle part); m. Pectoralis major; m. Lattissimus dorsi; m. Deltoideus anterior & m. Deltoideus posterior) front and back heads. Results: The most significant activation for the persons studied to exhibit m. Trapezius transversalis (65,49%) m. Latissimus dorsi (49,41%) and m. Deltoideus posterior (47,91%). Conclusions: the competitors' different technical skills differentiate some muscle activities, which will inevitably lead to different biomechanical expediency of the movements; The main direction in work should be to the muscles along the back of the trunk: Trapezius Transversalis, M. Latissimus dorsi, and m. Deltoideus posterior

Study of Body Composition and Obesity in Children Aged 12-14 Years

In the last decades, the topic of physical activity and the consequences of lack of movement among adolescents have been particularly relevant. The purpose of the current study is to determine the body composition and obesity of children in grades 7-12 and its relationship with their physical activity through body composition analysis and statistical procedures

History of the World Sleep Day

BackgroundSleep has also been cherished by society as a basic human need with a crucial importance for human health. People spend around one third of their lives sleeping. Nowadays, it has never been harder to achieve a restful sleep. When sleep is better understand, that will lessen the drawbacks of the different sleep disorders. Healthy sleep is important for maintaining physical and mental health in adult individuals. Sleep deprivation poses a significant risk for the individual and leads to psychological conditions, such as depression and anxiety. Several sleep disorders are known to the science. If breathing during sleep is not regular, a case of obstructive sleep apnea (OSA) may have been diagnosed.The World Sleep Day is traditionally celebrated in March, on the Friday before the Spring vernal equinox of each year. It is a global awareness and internationally recognized event, organized annually since 2008 by the World Sleep Day Committee of the World Sleep Society. Organizers aim to raise awareness of the problems with proper sleep, sleep disorders and aspects connected to it – medical, social, educational and others.MethodsScientific databases – PubMed, SCOPUS and MEDLINE were used to search for the information targeted. The following keywords – World Sleep Day, history, events, prophylaxis, sleep disorders were used. Information from the official websites of the societies involved in celebrating World Sleep Day was included as well.The aim of the following article is to study the history of the event from its foundation till today, aiming to stress out its usefulness.Results and discussionWorld Sleep Days has been internationally celebrated since 2008 for 15 years now. Since 2016, Bulgaria actively participates in all events organized by the World Sleep Society – Scientific symposiums, prophylactic check-ups for obstructive sleep apnea, elective disciplines in the teaching of students are organized. Importance is put on informing society about the dangers of undiagnosed and untreated sleep disorders, especially sleep apnea. Sleep medicine and Dental Sleep medicine are not recognized as medical specialties in the Republic of Bulgaria.ConclusionsProblems of sleep are extremely common in our days. The situation is continuously being worsened due to the hyperconnectivity people experience with the glowing computer and mobile phone screens. It is admirable that specialists in the field and society try to raise awareness and combat the poor sleep quality consequences. Only by doing the abovementioned, alleviation of the undesirable outcomes of irregular sleep can be reached. Legislative measures should be taken in order to certify Sleep medicine and Dental sleep medicine as medical specialties in theRepublic of Bulgaria

Using quantum key distribution for cryptographic purposes: a survey

The appealing feature of quantum key distribution (QKD), from a cryptographic viewpoint, is the ability to prove the information-theoretic security (ITS) of the established keys. As a key establishment primitive, QKD however does not provide a standalone security service in its own: the secret keys established by QKD are in general then used by a subsequent cryptographic applications for which the requirements, the context of use and the security properties can vary. It is therefore important, in the perspective of integrating QKD in security infrastructures, to analyze how QKD can be combined with other cryptographic primitives. The purpose of this survey article, which is mostly centered on European research results, is to contribute to such an analysis. We first review and compare the properties of the existing key establishment techniques, QKD being one of them. We then study more specifically two generic scenarios related to the practical use of QKD in cryptographic infrastructures: 1) using QKD as a key renewal technique for a symmetric cipher over a point-to-point link; 2) using QKD in a network containing many users with the objective of offering any-to-any key establishment service. We discuss the constraints as well as the potential interest of using QKD in these contexts. We finally give an overview of challenges relative to the development of QKD technology that also constitute potential avenues for cryptographic research.Comment: Revised version of the SECOQC White Paper. Published in the special issue on QKD of TCS, Theoretical Computer Science (2014), pp. 62-8

A Novel approach to quality-of-service provisioning in trusted relay quantum key distribution networks

In recent years, noticeable progress has been made in the development of quantum equipment, reflected through the number of successful demonstrations of Quantum Key Distribution (QKD) technology. Although they showcase the great achievements of QKD, many practical difficulties still need to be resolved. Inspired by the significant similarity between mobile ad-hoc networks and QKD technology, we propose a novel quality of service (QoS) model including new metrics for determining the states of public and quantum channels as well as a comprehensive metric of the QKD link. We also propose a novel routing protocol to achieve high-level scalability and minimize consumption of cryptographic keys. Given the limited mobility of nodes in QKD networks, our routing protocol uses the geographical distance and calculated link states to determine the optimal route. It also benefits from a caching mechanism and detection of returning loops to provide effective forwarding while minimizing key consumption and achieving the desired utilization of network links. Simulation results are presented to demonstrate the validity and accuracy of the proposed solutions

Improvement of continuous-variable quantum key distribution systems by using optical preamplifiers

Continuous-variable quantum key distribution protocols, based on Gaussian modulation of the quadratures of coherent states, have been implemented in recent experiments. A present limitation of such systems is the finite efficiency of the detectors, which can in principle be compensated for by the use of classical optical preamplifiers. Here we study this possibility in detail, by deriving the modified secret key generation rates when an optical parametric amplifier is placed at the output of the quantum channel. After presenting a general set of security proofs, we show that the use of preamplifiers does compensate for all the imperfections of the detectors when the amplifier is optimal in terms of gain and noise. Imperfect amplifiers can also enhance the system performance, under conditions which are generally satisfied in practice.Comment: 11 pages, 7 figures, submitted to J. Phys. B (special issue on Few Atoms Optics

Field test of a continuous-variable quantum key distribution prototype

We have designed and realized a prototype that implements a continuous-variable quantum key distribution protocol based on coherent states and reverse reconciliation. The system uses time and polarization multiplexing for optimal transmission and detection of the signal and phase reference, and employs sophisticated error-correction codes for reconciliation. The security of the system is guaranteed against general coherent eavesdropping attacks. The performance of the prototype was tested over preinstalled optical fibres as part of a quantum cryptography network combining different quantum key distribution technologies. The stable and automatic operation of the prototype over 57 hours yielded an average secret key distribution rate of 8 kbit/s over a 3 dB loss optical fibre, including the key extraction process and all quantum and classical communication. This system is therefore ideal for securing communications in metropolitan size networks with high speed requirements.Comment: 15 pages, 6 figures, submitted to New Journal of Physics (Special issue on Quantum Cryptography

Field test of quantum key distribution in the Tokyo QKD Network

A novel secure communication network with quantum key distribution in a metropolitan area is reported. Different QKD schemes are integrated to demonstrate secure TV conferencing over a distance of 45km, stable long-term operation, and application to secure mobile phones.Comment: 21 pages, 19 figure

Controlling passively-quenched single photon detectors by bright light

Single photon detectors based on passively-quenched avalanche photodiodes can be temporarily blinded by relatively bright light, of intensity less than a nanowatt. I describe a bright-light regime suitable for attacking a quantum key distribution system containing such detectors. In this regime, all single photon detectors in the receiver Bob are uniformly blinded by continuous illumination coming from the eavesdropper Eve. When Eve needs a certain detector in Bob to produce a click, she modifies polarization (or other parameter used to encode quantum states) of the light she sends to Bob such that the target detector stops receiving light while the other detector(s) continue to be illuminated. The target detector regains single photon sensitivity and, when Eve modifies the polarization again, produces a single click. Thus, Eve has full control of Bob and can do a successful intercept-resend attack. To check the feasibility of the attack, 3 different models of passively-quenched detectors have been tested. In the experiment, I have simulated the intensity diagrams the detectors would receive in a real quantum key distribution system under attack. Control parameters and side effects are considered. It appears that the attack could be practically possible.Comment: Experimental results from a third detector model added. Minor corrections and edits made. 11 pages, 10 figure

Topological optimization of quantum key distribution networks

A Quantum Key Distribution (QKD) network is an infrastructure that allows the realization of the key distribution cryptographic primitive over long distances and at high rates with information-theoretic security. In this work, we consider QKD networks based on trusted repeaters from a topology viewpoint, and present a set of analytical models that can be used to optimize the spatial distribution of QKD devices and nodes in specific network configurations in order to guarantee a certain level of service to network users, at a minimum cost. We give details on new methods and original results regarding such cost minimization arguments applied to QKD networks. These results are likely to become of high importance when the deployment of QKD networks will be addressed by future quantum telecommunication operators. They will therefore have a strong impact on the design and requirements of the next generation of QKD devices.Comment: 25 pages, 4 figure