Mass Dampers with Limited Amplitude

Mass dampers are widely used in engineering applications. We consider the effects of limitations on the damper amplitude. Using simple methods to analyze very general mass dampers, we find an upper limit to the damping. The maximum damping logarithmic decrement is δmax = 4μα, where μ is the mass ratio, and α isthe amplitude ratio of damper to structure amplitude. The result is further discussed in relation to Tuned Mass Dampers (TMDs), which can performvery well if there is enough avaliable space. In practice, amplitude limits always apply, and our result can be used to relate these to the damper performance.Our result also applies to active devices, which have to obey the limit mentioned above. Simulated tests of TMDs and other mass dampers are described. The damping is measured both by decay tests and by forced motion test. The methods agree well in the amplitude-limited regime. In other cases, decay tests are difficulet to interpret, indicating that one needs to be very careful whenmeasuring damping of 2DOF systems based solely on decay tests. We hope that our result may inform the selection and design of mass dampers in the future, where one should consider amplitude limits as the very first step.

COMPOSITION AND CONTENT OF ORGANIC ACIDS IN JUICE AND WINE FROM GRAPES GROWN IN THE NORTH-WESTERN ZONE OF DAGESTAN

Методом капиллярного электрофореза изучен качественный состав и количественное содержание органических кислот в соках и виноматериалах из винограда сортов Ркацители и Молдова, выращенных в экологических условиях равнины и предгорья северо-западной зоны Дагестана. Идентифицировано восемь компонентов: винная, лимонная, молочная, муравьиная, уксусная, щавелевая, яблочная и янтарная кислоты. Превалировали винная и яблочная кислоты, которые, как и уксусная, содержались во всех опытных образцах. Количество обнаруженных органических кислот составляло от 0,01 (молочная и янтарная) до 3,31 г/дм3 (винная). Их наибольшая общая массовая концентрация определена в соке из винограда сорта Ркацители – 5,3 г/дм3. Отмечено, что суммарное содержание этих компонентов в образцах соков и виноматериалов из винограда сортов Ркацители и Молдова незначительно зависит от высоты места произрастания винограда над уровнем моря. Этот природный фактор обусловливает различия в соотношениях кислот, особенно при формировании их пулов в виноматериалах. Органические кислоты, обнаруженные в исследованных образцах продуктов переработки винограда, способны влиять на появление неординарных нюансов цвета, вкуса и аромата, повышающих качество шампанских вин и коньяков. The qualitative composition and quantitative content of organic acids in juices and wine materials from grapes of Rkatsiteli and Moldova grown under the ecological conditions of the plains and foothills of the North West zone of Dagestan were studied by the method of capillary electrophoresis. Eight components are identified: wine, lemon, dairy, ant, acetic, oxalic, apple and amber acids. The amount of the found organic acids was 0,01 (dairy and amber acids) – 3,31 g/dm3 (wine acid). Their highest general mass concentration is defined in juice from Rkatsiteli – 5,3 g/dm3. It is noted that the total content of these components in the samples of juice and wine materials from grapes of Rkatsiteli and Moldova slightly depends on the height of your growing grapes above the sea level. This natural factor causes differences in ratios of acids, especially when forming their pools in wine materials. The organic acids found in the studied products of processing made from Rkatsiteli and Moldova grapes are capable to influence emergence of the extraordinary nuances of color, taste and aroma increasing quality of sparkling wines and cognacs.

Scattering amplitudes for all masses and spins

We introduce a formalism for describing four-dimensional scattering amplitudes for particles of any mass and spin. This naturally extends the familiar spinor-helicity formalism for massless particles to one where these variables carry an extra SU(2) little group index for massive particles, with the amplitudes for spin S particles transforming as symmetric rank 2S tensors. We systematically characterise all possible three particle amplitudes compatible with Poincare symmetry. Unitarity, in the form of consistent factorization, imposes algebraic conditions that can be used to construct all possible four-particle tree amplitudes. This also gives us a convenient basis in which to expand all possible four-particle amplitudes in terms of what can be called “spinning polynomials”. Many general results of quantum field theory follow the analysis of four-particle scattering, ranging from the set of all possible consistent theories for massless particles, to spin-statistics, and the Weinberg-Witten theorem. We also find a transparent understanding for why massive particles of sufficiently high spin cannot be “elementary”. The Higgs and Super-Higgs mechanisms are naturally discovered as an infrared unification of many disparate helicity amplitudes into a smaller number of massive amplitudes, with a simple understanding for why this can’t be extended to Higgsing for gravitons. We illustrate a number of applications of the formalism at one-loop, giving few-line computations of the electron (g − 2) as well as the beta function and rational terms in QCD. “Off-shell” observables like correlation functions and form-factors can be thought of as scattering amplitudes with external “probe” particles of general mass and spin, so all these objects — amplitudes, form factors and correlators, can be studied from a common on-shell perspective.

Design rules for timber log reciprocal floors, based on mass optimization under stiffness constraint

Building with raw timber allows to reduce the price of construction and to make it more competitive with respect to concrete or steel construction. For a few years now, the combination of parametric design and robotic tools make possible the fast and precise milling of timber logs for their accurate connection. However, the spans are quickly limited by the logs length. In this context, reciprocal structures are relevant, since they allow to build large spans structures with short beams. Finally, the architectural interest of reciprocal structures is not to prove. However, the choice of the most efficient reciprocal frame, as well as its structural relevance in terms of mass and stiffness is, most of the time, ruled by subjective considerations. This paper focuses on rectangular floors composed of reciprocal moduli and has three objectives: (1) to develop a general mass and stiffness optimization method for reciprocal floors, which is not only necessary to limit the price, but also to reduce their thickness, (2) to define design rules for reciprocal floors, in particular for the choice of the best engagement ratio, and (3) to compare the structural efficiency of reciprocal floors with the one of “traditional” floors with parallel logs. Coming from a dimensionless transformation of the equilibrium equations, the results of this article will thus give the designers keys to better design reciprocal structures, evaluate their structural performances and relevance, and justify their choices.

Silent SARS-CoV-2 Infections, Waning Immunity, Serology Testing, and COVID-19 Vaccination: A Perspective

Severe acute respiratory syndrome coronavirus 2 (SARS-CoV-2) virus causes a spectrum of clinical manifestations, ranging from asymptomatic to mild, moderate, or severe illness with multi-organ failure and death. Using a new machine learning algorithm developed by us, we have reported a significantly higher number of predicted COVID-19 cases than the documented counts across the world. The sole reliance on confirmed symptomatic cases overlooking the symptomless COVID-19 infections and the dynamics of waning immunity may not provide ‘true’ spectrum of infection proportion, a key element for an effective planning and implementation of protection and prevention strategies. We and others have previously shown that strategic orthogonal testing and leveraging systematic data-driven modeling approach to account for asymptomatics and waning cases may situationally have a compelling role in informing efficient vaccination strategies beyond prevalence reporting. However, currently Centers for Disease Control and Prevention (CDC) does not recommend serological testing either before or after vaccination to assess immune status. Given the 27% occurrence of breakthrough infections in fully vaccinated (FV) group with many being asymptomatics and still a larger fraction of the general mass remaining unvaccinated, the relaxed mask mandate and distancing by CDC can drive resurgence. Thus, we believe it is a key time to focus on asymptomatics (no symptoms) and oligosymptomatics (so mild that the symptoms remain unrecognized) as they can be silent reservoirs to propagate the infection. This perspective thus highlights the need for proactive efforts to reevaluate the current variables/strategies in accounting for symptomless and waning fractions.

Elite Marathoners Run Faster With Increasing Temperatures in Berlin Marathon

The influence of environmental conditions has been investigated for different marathon races, but not for the Berlin Marathon, the fastest marathon race course in the world. The aim of this study was to investigate the potential influence of environmental conditions such as temperature, precipitation, sunshine, and atmospheric pressure on marathon race times in the Berlin Marathon since its first event in 1974–2019. A total of n = 882,540 valid finisher records were available for analysis, of which 724,135 correspond to male and 158,405 to female runners. We performed analyses regarding performance levels considering all finishers, the top 3, the top 10, and the top 100 women and men. Within the 46 years of Berlin marathons under study, there was some level of precipitation for 18 years, and 28 years without any rain. Sunshine was predominant in 25 of the events, whilst in the other 21, cloud cover was predominant. There was no significant trend with time in any of the weather variables (e.g., no increase in temperature across the years). Overall runners became slower with increasing temperature and sunshine duration, however, elite runners (i.e., top 3 and top 10) seemed to run faster and improved their race times when the temperature increased (with women improving more than men). Top 10 women seemed to benefit more from increasing temperatures than top 10 males, and male top 100 runners seemed to benefit more from increasing temperatures than female top 100 runners. In the top three sub-group, no differences were observed between male and female correlations. In summary, in marathoners competing in the Berlin Marathon between 1974 and 2019, increasing temperatures and sunshine duration showed a different effect on different performance levels where overall runners (i.e., the general mass of runners) became slower with increasing temperature and sunshine duration, but elite runners (i.e., top 3, top 10) became faster with increasing temperatures where sex differences exist.

Vector dark matter from a gauged SU(2) symmetry

We propose a scenario of dark sector described by a hidden SU(2) gauge symmetry which is broken by a vacuum expectation value(VEV) of a scalar multiplet. We discuss a general mass relation among SU(2) gauge bosons after spontaneous symmetry breaking which is determined by weight of gauge group representation associated with a scalar multiplet developing VEV. Then a model with quintet and triplet scalar fields is discussed in which hidden gauge boson can be dark matter(DM) stabilized by remnant discrete Z2 symmetry and resonant dark matter annihilation is realized by mass relation between DM and mediator. We estimate relic density and spin independent DM-nucleon scattering cross section searching for allowed parameter region.

Beliefs in Conspiracy Theories and Misinformation About COVID-19: Comparative Perspectives on the Role of Anxiety, Depression and Exposure to and Trust in Information Sources

While COVID-19 spreads aggressively and rapidly across the globe, many societies have also witnessed the spread of other viral phenomena like misinformation, conspiracy theories, and general mass suspicions about what is really going on. This study investigates how exposure to and trust in information sources, and anxiety and depression, are associated with conspiracy and misinformation beliefs in eight countries/regions (Belgium, Canada, England, Philippines, Hong Kong, New Zealand, United States, Switzerland) during the COVID-19 pandemic. Data were collected in an online survey fielded from May 29, 2020 to June 12, 2020, resulting in a multinational representative sample of 8,806 adult respondents. Results indicate that greater exposure to traditional media (television, radio, newspapers) is associated with lower conspiracy and misinformation beliefs, while exposure to politicians and digital media and personal contacts are associated with greater conspiracy and misinformation beliefs. Exposure to health experts is associated with lower conspiracy beliefs only. Higher feelings of depression are also associated with greater conspiracy and misinformation beliefs. We also found relevant group- and country differences. We discuss the implications of these results.