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Introduction: Early school-aged children are in a transitional phase from primary to permanent dentition. Established dietary and oral hygiene habits will influence the condition of the oral cavity in the future., Aim: This study aimed to evaluate alterations in early school children's dietary and oral hygiene practices during the COVID-19 pandemic and to anticipate potential long-term health implications., Material and Methods: This cross-sectional online study involved guardians of Polish children aged 6-10 years, living in Western Poland, who were socially isolated at home during the COVID-19 pandemic. A total of 180 guardians were invited to participate in this study. The questionnaire included 17 questions divided into four different sections-the child's anthropometric data, dietary habits, oral health, and attitude to dental visits., Results: The survey was completed by 106 guardians. The mean (standard deviation) age of the children was 8.12 (0.93) years (range 6-10 years). Overall, 24.5% of the surveyed individuals reported buying healthy products (fresh vegetables, fruit) more frequently during the pandemic. Furthermore, 35.8% admitted to snacking between meals more frequently and 16.0% less frequently. Almost one-quarter of the parents acknowledged that their children were less motivated to maintain oral hygiene during the pandemic and 28.3% declared a lower frequency of visits to the dentist from the outbreak of the pandemic for two main reasons: a fear of coronavirus transmission and economic reasons., Conclusions: In the group studied, the results of the assessment indicate that the COVID-19 pandemic had some effects on oral health that may lead to an increased risk of oral disease development, such as tooth decay in children. None of the respondents noticed an increase in their child's motivation about good oral hygiene despite spending more time at home. The irregularity of follow-up visits for one-third of the respondents hindered preventive measures and the continuation of dental treatment.

The incommensurately modulated antiferroelectric phase of sodium nitrite, NaNO2, transforms at T(N) = 437.7 K to the short-range modulated paraelectric phase. The apparently discontinuous phase transition is accompanied by characteristic changes in the diffraction pattern. Contrary to the well known modulated structures with sharp satellite reflections, the diffraction pattern of a short-range modulated structure contains diffuse satellite reflections. The short-range modulated crystal structure of the paraelectric phase of sodium nitrite has been analysed by the Reverse Monte Carlo (RMC) simulation of X-ray diffuse scattering. The crystal structure of sodium nitrite may be regarded as consisting of [Na+NO2-]infinity rows running along the polar b axis. One can expect long fragments of rows with uniform polarity The assumption that single [Na+NO2-]infinity rows are polar with uniform polarity proved to be a convenient approximation which is in good agreement with the observed diffraction pattern. The distribution of (+)- and (-)-[Na+NO2-]infinity polar rows crossing the (010) plane of short-range modulated NaNO2 revealed by RMC shows nanodomains consisting of distorted fragments of a sinusoidally modulated crystal structure. The size of the nanodomains and the degree of order in paraelectric NaNO2 decreases with temperature.

Crystals of uranium iodine phthalocyanine present an example of a disordered commensurate modulated structure of the intergrowth type. The short-range order of both uranium ions and iodine chains [I(3)(-)](n) has been analysed by Reverse Monte Carlo (RMC) simulation of X-ray diffuse scattering. The diffraction pattern of uranium iodine phthalocyanine contains diffuse superstructure reflections. In the routine crystal structure analysis diffuse superstructure reflections may be either omitted or measured and classified along with other Bragg reflections. The crystal structure of uranium iodine phthalocyanine is an example of such ambiguity. The crystal structures of two specimens of [U(1-x)Pc(2)]I(2-y) with slightly different composition have been published in the literature with different space groups and unit cells. We have shown that the structure of both specimens differs only in the degree of short-range order and is isostructural with [YbPc(2)]I(2). We have also shown that while the omission of diffuse reflections results in the average crystal structure, the treatment of these reflections as normal Bragg reflections is incorrect and produces the structure averaged over a limited small range.

Iodine-doped ytterbium phthalocyanine, C(64)H(32)N(16)YbI(2), [YbPc(2)]I(2) (YPI), presents an example of a disordered modulated crystal structure of the intergrowth type. The short-range order in YPI has been studied at ambient temperature by the diffuse X-ray scattering technique. Both Yb and I atoms are disordered. In a unit cell of the average structure, the Yb atoms occupy two positions, 1/2, 1/2, 1/4 or 1/2, 1/2, 3/4, with occupancy 0.5. In the neighbouring unit cells in the (001) plane there is, however, a strong tendency towards an alternating distribution of ytterbium in positions shifted by Delta z = 1/2. The crystal structure of YPI consists of one-dimensional columnar stacks of [YbPc(2)(2/3+)](n) and of linear iodine chains [I(3)(-)](n). The modulation is commensurate since the period c(I) of iodine chains [I(3)(-)](n) in the [001] direction is equal to one-half of the period c of the [YbPc(2)(2/3+)](n) stacks. In the crystal structure, each stack of [YbPc(2)(2/3+)](n) may occur in two settings shifted by c/2 and each iodine chain in three settings shifted along [001] by one-third of the period c(I). The short-range order of iodine chains distributed over three settings results in a complicated pattern. Iodine chains of the same setting tend to form ribbons perpendicular to <100> and running along [001].

The temperature dependence of the X- and Q-band EPR spectra of Cs(2)[Zn(H(2)O)(6)](ZrF(6))(2) containing approximately 1% Cu(2+) is reported. All three molecular g-values vary with temperature, and their behavior is interpreted using a model in which the potential surface of the Jahn-Teller distorted Cu(H(2)O)(6)(2+) ion is perturbed by an orthorhombic "strain" induced by interactions with the surrounding lattice. The strain parameters are significantly smaller than those reported previously for the Cu(H(2)O)(6)(2+) ion in similar lattices. The temperature dependence of the two higher g-values suggests that in the present compound the lattice interactions change slightly with temperature. The crystal structure of the Cs(2)[Zn(H(2)O)(6)](ZrF(6))(2) host is reported, and the geometry of the Zn(H(2)O)(6)(2+) ion is correlated with lattice strain parameters derived from the EPR spectrum of the guest Cu(2+) complex.