Transmission of severe acute respiratory syndrome coronavirus-2 (SARS-CoV-2) is possible among symptom-free individuals. Patients are avoiding medically necessary healthcare visits for fear of becoming infected in the healthcare setting. We screened 489 symptom-free healthcare workers for SARS-CoV-2 and found no positive results, strongly suggesting that the prevalence of SARS-CoV-2 was <1%.

The chemical stabilities of mendipite, Pb3O2Cl2, diaboleïte, Pb2CuCl2(OH)4, chloroxiphite, Pb3CuCl2O2(OH)2, and cumengéite, Pb19Cu24Cl42 (OH)44, have been determined in aqueous solution at 298.2 K. Values of standard Gibbs free energy of formation, ΔGf°, for the four minerals are −740, −1160, −1129, and −15163±20 kJ mol−1 respectively. These values have been used to construct the stability diagram shown in fig. I which illustrates their relationships to each other and to the minerals cotunnite, PbCl2, paralaurionite, PbOHCl, and litharge, PbO. This diagram shows that mendipite occupies a large stability field and should readily form from cold, aqueous, mineralizing solutions containing variable amounts of lead and chloride ions, and over a broad pH range. The formation of paralaurionite and of cotunnite requires a considerable increase in chloride ion concentration, although paralaurionite can crystallize under much less extreme conditions than cotunnite. The encroachment of the copper minerals on to the stability fields of those mineral phases containing lead(II) only is significant even at very low relative activities of cupric ion. Chloroxiphite has a large stability field, and at given concentrations of cupric ion, diaboleïte is stable at relatively high aCl−. Cumengéite will only form at high concentrations of chloride ion.

Large trace fossils attributed to the ichnogenus Psilonichnus (Fürsich) have been identified in subtidal sediments of the Red Crag Formation (late Pliocene) of Walton-on-the-Naze, Essex, U.K. The traces are vertical or inclined, tapering cylindrical structures, occasionally branched, up to 2.3 m long. The structures are mud-rich relative to the surrounding sediment and their fills often show a spiralling grain fabric. The ichnogenus Psilonichnus has formerly been attributed to the burrowing activities of intertidal and supratidal crab species. The known fossil crab assemblage of the Red Crag contains no deep burrowing species. The traces are thus attributed to other crustaceans, possibly thalassinidean shrimps. The occurrence indicates that Psilonichnus may have a greater palaeoenvironmental range than previously realized.

Background: Patients with Rett syndrome (RTT) may demonstrate parkinsonian features. Here, we report a preliminary cross-sectional and prospective evaluation of the evolution, regional distribution, and eventual incidence of rigid tone in a cohort of MECP2 mutation-positive patients. Methods: In 51 participants, muscle tone rigidity in extremity regions and neck plus hypomimia were quantified using an RTT rigidity distribution (RTTRD) score with a range of 0 to 15. RTTRD scores were correlated with age, ability to walk and speak, mutation type, and, in a small subgroup (n=9), cerebrospinal fluid (CSF) homovanillic acid (HVA) and 5-hydroxyindole-acetic acid levels. Results: Participant ages ranged from 2 years and 5 months, to 54 years. Rigidity was found in 43/51 (84.3%); it appeared as early as age 3, increased in extent with age, and was present in all participants aged ≥13. Ankle region rigidity appeared first, followed by proximal legs, arms, neck, and face. Ambulatory participants (n=21) had lower RTTRD scores than nonambulatory (n=30; p=0.003). We found a trend to lower scores in participants with retained speech (n=13) versus those with none (n=38; p=0.074), and no difference in scores for those with truncating (n=25) versus missense mutations (n=22; p=0.387). RTTRD scores correlated negatively with CSF HVA levels (R=−0.83; p=0.005), but not with 5-hydroxyindole-acetic acid levels (R=−0.45; p=0.22). Conclusions: Although assessment of muscle tone is somewhat subjective and the RTTRD has not been validated, this study nevertheless suggests that parkinsonian rigidity in RTT is common and frequently increases in extent with age; its severity correlates directly with impaired ambulation and inversely with CSF HVA levels.

On rare occasions anticonvulsant medication may cause severe or fatal toxic reactions. This position paper, approved by the Canadian Association for Child Neurology, examines the value of routine blood and urine screening to prevent catastrophic reactions in asymptomatic patients. The basic assumptions of such a screening program are faulty or unproven. Although not definitive, available studies of screening do not appear to support its value. It is recommended that routine blood and urine screening be discontinued in asymptomatic patients. Until such time as further research is able to identify patients at special risk, it is suggested that patients be carefully informed of the early symptoms of severe toxic reactions and report these immediately to a physician.

Social scientists generally enjoy substantial latitude in selecting measures and models for hypothesis testing. Coupled with publication and related biases, this latitude raises the concern that researchers may intentionally or unintentionally select models that yield positive findings, leading to an unreliable body of published research. To combat this “fishing” problem in medical studies, leading journals now require preregistration of designs that emphasize the prior identification of dependent and independent variables. However, we demonstrate here that even with this level of advanced specification, the scope for fishing is considerable when there is latitude over selection of covariates, subgroups, and other elements of an analysis plan. These concerns could be addressed through the use of a form of comprehensive registration. We experiment with such an approach in the context of an ongoing field experiment for which we drafted a complete “mock report” of findings using fake data on treatment assignment. We describe the advantages and disadvantages of this form of registration and propose that a comprehensive but nonbinding approach be adopted as a first step to combat fishing by social scientists. Likely effects of comprehensive but nonbinding registration are discussed, the principal advantage being communication rather than commitment, in particular that it generates a clear distinction between exploratory analyses and genuine tests.

This paper reviews a selection of nine indicators for assessing the biological state of a fish population monitored only by using trawl surveys in which catchability is assumed constant from time to time and place to place. The intention is to inform or remind of the range of possibilities and of associated practical and statistical issues. The indicators, grouped according to relationships with abundance, length, age, weight, and reproduction, are documented in a standard format covering estimation, interpretability, sensitivity, considerations for reference points where possible, and an example of their application. Lastly, selected indicators together with year-class curves fitted to abundance indices-at-age are applied to the North Sea cod to demonstrate the feasibility of an assessment based on only one trawl survey. Results support findings of the International Council for the Exploration of the Sea (ICES) working group on the assessment of demersal stocks in the North Sea and Skagerrak.