Non-destructive handheld XRF study of archaeological composite silver objects—the case study of the late Roman Seuso Treasure

This study details the non-destructive chemical analysis of composite silver objects (ewers, situlas, amphora and casket) from one of the most significant late Roman finds, the Seuso Treasure. The Seuso Treasure consists of fourteen large silver vessels that were made in the fourth–early fifth centuries AD and used for dining during festive banquets and for washing and beautification. The measurements were systematically performed along a pre-designed grid at several points using handheld X-ray fluorescence analysis. The results demonstrate that all the objects were made from high-quality silver (above 90 wt% Ag), with the exception of the base of the Geometric Ewer B. Copper was added intentionally to improve the mechanical properties of soft silver. The gold and lead content of the objects shows constant values (less than 1 wt% Au and Pb). The chemical composition as well as the Bi/Pb ratio suggests that the parts of the composite objects were manufactured from different silver ingots. The ewers were constructed in two ways: (i) the base and the body were made separately, or (ii) the ewer was raised from a single silver sheet. The composite objects were assembled using three methods: (i) mechanical attachment; (ii) low-temperature, lead-tin soft solders; or (iii) high-temperature, copper-silver hard solders. Additionally, two types of gilding were revealed by the XRF analysis, one with remnants of mercury, i.e. fire-gilding, and another type without remnants of mercury, presumably diffusion bonding.

Electrostatic mechanisms for the spread of coronaviruses

Clothing of a person in motion electrifies and causes around his body intensive reproduction of particles of air ions, atoms, and air molecules, aerosols (similar in size to particles of coronaviruses), which are non-contact, in moments of discharge from clothing, currents of displacement and transmission (or air flow) are transferred to the environment, similar to the processes of inhalation of electroaerosols or powder. Waveform recorded outbreaks of coronal discharges (CD) - (pulses of more than 25.0 kV/m) the electrostatic field intensity tension (EFI) recorded by the IRI-04M device on human clothing in casual clothing and shoes, and non-contact (0.4-1.2) m of communication of people in the process of movement in the winter road. In the process of human interaction in antistatic clothing and footwear, current emissions (pulses less than 3.0 kV/m), almost not recorded, indicates the absence of outbreaks of CD. The most likely mechanical attachment (the first phase of absorption) to the target cell was shown to be performed by negatively charged (rather than neutral) particles of coronaviruses. The peak of the spread of coronaviruses in the premises occurs in the conditions of the heating period. In the environment, the peak of distribution depends on seasonal conditions of atmospheric electricity - in autumn and spring higher, in winter and summer being 3-5 times lower. Recommendations are given to normalize anti-static conditions in the premises and to monitor the safety of the clothes of the medical worker at the entrance to the danger zone. The method, the self-control tool (the instrument IRI-04M, located on the sternum of the body) and the criterion of safe electrification of the human - a tension of less than 4.5 kV/m, when there is still no reproduction and transfer of coronavirus particles with a diameter of more than 30 nm.

Primary stability achieved during implant surgery and bone loss at recovery in patients of a private dental institution — A retrospective analysis

Implant stability plays a critical role for osseointegration, without osseointegration long term success cannot be achieved, primary stability occurs from mechanical attachment with the cortical bone. It is the gold standard for success of implants. This is a descriptive clinical study carried out in saveetha dental college and hospital, Poonamallee, Chennai. All the patients who underwent single or two-unit implant surgery were selected. The study setting was done from university predominantly south Indian populations and data with regard to primary stability at placement, level of the implant with bone, crestal bone loss at stage 2 recovery were retrieved from the digital case sheets. Data were entered using SPSS software, and Chi-square test was used for inferential analysis, with a P-value < 0.05 was said to be statistically significant. The results obtained indicate more implants are placed with primary stability in 30-40 Ncm(49.8%). More frequently placed crestal relation is equi crestal region (84.4%) and crestal bone loss was less than 1-2mm is seen(87.3%) at stage 2 recovery. The results were subjected to statistical chi-square test, and it is observed that primary stability at 30-40 Ncm or greater did not have any significant association with crestal bone loss. An equi crestal placement of the implant was preferred irrespective of implant type.

Investigations on Stresses in Optical Components with Spherical Surfaces

The paper has substantiated an expediency to fix lenses with a thin center (biconcave, flat concave and negative meniscus) to a non-operational cylindrical surface. This avoids their temperature distortion at the blocking stage which is a reason for occurrence of irremovable micro and macro errors on executive surfaces of a component after its unblocking and it causes astigmatism in an image which is formed by an optical-electronic device. The paper considers a method for attachment of a lens to its side surface and it contains a design description of the device for mechanical attachment of the studied lenses during their simultaneous double-sided abrasive processing under free-grinding conditions. The paper presents a methodology for determination of a stressed state in lenses, which is based on a mathematical model of a uniform elastic isotropic deformation of a solid body. This approach takes into account a finite element method which consists in an approximation of a body under study with the help of a model presenting a set of elements with a finite number of freedom degrees which are interrelated at node points. The investigations have been executed with the purpose to study a nature of deformation distribution in a lens which made it possible to establish a directly proportional dependence of displacements in the center of the part on the magnitude of clamping forces. The paper reveals an insignificant influence of a clamping force magnitude and elastic characteristics of a lens on an optimum position of an application plane of its clamping forces. A non-contact method for monitoring errors on a polished lens surface using an interferometer with a reference front surface has been proposed in the paper.