Patient: Male, 55-year-old Final Diagnosis: COVID 19 infection • deep neck infection • pyogenic arthritis Symptoms: Neck pain • shoulder pain Medication: Antibiotics Clinical Procedure: Incisional drainage Specialty: Otolaryngology Objective: Unusual clinical course Background: COVID-19 is treated using antiviral and immunosuppressive drugs. Therefore, patients treated for COVID-19 may have an increased risk of secondary infection and a masked inflammatory response. We present a case of a deep neck abscess caused by pyogenic sternoclavicular arthritis during treatment for COVID-19. Case Report: A 55-year-old man with COVID-19 was admitted to the hospital with hypoxemia. He was then treated with remdesivir, tocilizumab, and dexamethasone and was placed in the prone position. When his condition stabilized, pain in the left shoulder appeared. There was no fever or elevation in inflammation markers, and he was administered analgesics. However, the pain worsened and redness of the left neck appeared. Plain computed tomography (CT) showed swelling of the left neck muscles. Because cellulitis was suspected, he was treated with antibiotics, but his symptoms did not improve. Three days after the plain CT, contrast-enhanced CT showed sternoclavicular arthritis, deep neck abscess, and mediastinal abscess. Therefore, an emergency incisional drainage was performed under general anesthesia. Wound cleaning and drainage were continued after surgery, and after drainage tubes were removed, the patient was discharged on postoperative day 17. Conclusions: Cervical infections after COVID-19 treatment have been reported in a few cases. Particularly, deep neck abscesses require more attention since they could be fatal if not treated immediately. If a secondary infection is suspected in a patient treated with immunosuppressive drugs for COVID-19, a thorough physical examination should be performed to avoid misdiagnosis.

It is known that intuitionistic Kripke semantics can be generalized so that it can treat arbitrary propositional connectives characterized by truth functions. We extend this generalized Kripke semantics to first-order logic, and study how the choice of connectives changes the relation between intuitionistic predicate logic and the logic of constant domains in terms of validity of sequents. Our main result gives a simple necessary and sufficient condition for the set of valid sequents in intuitionistic predicate logic to coincide with the set of valid sequents in the logic of constant domains.

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Regarding strictly monadic second-order logic (SMSOL), which is the fragment of monadic second-order logic in which all predicate constants are unary and there are no function symbols, we show that a standard deductive system with full comprehension is sound and complete with respect to standard semantics. This result is achieved by showing that in the case of SMSOL, the truth value of any formula in a faithful identity-standard Henkin structure is preserved when the structure is "standardized"; that is, the predicate domain is expanded into the set of all unary relations. In addition, we obtain a simpler proof of the decidability of SMSOL.

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