Mapped Null Hypersurfaces and Legendrian Maps

For an $(m+1)$-dimensional space-time $(X^{m+1}, g),$ define a mapped null hypersurface to be a smooth map $\nu:N^{m}\to X^{m+1}$ (that is not necessarily an immersion) such that there exists a smooth field of null lines along $\nu$ that are both tangent and $g$-orthogonal to $\nu.$ We study relations between mapped null hypersurfaces and Legendrian maps to the spherical cotangent bundle $ST^*M$ of an immersed spacelike hypersurface $\mu:M^m\to X^{m+1}.$ We show that a Legendrian map \wt \lambda: L^{m-1}\to (ST^*M)^{2m-1} defines a mapped null hypersurface in $X.$ On the other hand, the intersection of a mapped null hypersurface $\nu:N^m\to X^{m+1}$ with an immersed spacelike hypersurface $\mu':M'^m\to X^{m+1}$ defines a Legendrian map to the spherical cotangent bundle $ST^*M'.$ This map is a Legendrian immersion if $\nu$ came from a Legendrian immersion to $ST^*M$ for some immersed spacelike hypersurface $\mu:M^m\to X^{m+1}.$Comment: 13 pages, 1 figur

The Skylab concentrated atmospheric radiation project

The author has identified the following significant results. Comparison of several existing infrared radiative transfer models under somewhat controlled conditions and with atmospheric observations of Skylab's S191 and S192 radiometers illustrated that the models tend to over-compute atmospheric attenuation in the window region of the atmospheric infrared spectra

Theory of Linear Spin Wave Emission from a Bloch Domain Wall

We report an analytical theory of linear emission of exchange spin waves from a Bloch domain wall, excited by a uniform microwave magnetic field. The problem is reduced to a one-dimensional Schr\"odinger-like equation with a P\"oschl-Teller potential and a driving term of the same profile. The emission of plane spin waves is observed at excitation frequencies above a threshold value, as a result of a linear process. The height-to-width aspect ratio of the P\"oschl-Teller profile for a domain wall is found to correspond to a local maximum of the emission efficiency. Furthermore, for a tailored P\"oschl-Teller potential with a variable aspect ratio, particular values of the latter can lead to enhanced or even completely suppressed emission.Comment: added ancillary file

Studies with a spontaneous mouse tumor. I. Growth in normal mice and response to Corynebacterium parvum.

Growth of isogeneic transplants of a spontaneous murine adenocarcinoma, which is virtually devoid of tumour-specific transplantation antigens, is inhibited by i.v. injection of C. parvum 3 days after tumour inoculation, or by mixing a small dose of C. parvum with the tumour inoculum. Moreover, the therapeutic effect of cyclophosphamide, followed by i.v. or i.p. injection of C. parvum 5 days later, on established transplants of the same tumour is greater than that of cyclophosphamide alone. These findings are consistent with the hypothesis that in both situations (i.e. before the appearance of a palpable tumour and after reduction of an established tumour transplant with cyclophosphamide) the effect of C. parvum is largely due to activation of macrophages or macrophage precursors. They have the important practical implication that adjuvant therapy with C. parvum may be of value, even with tumours which are devoid of TSTA

Stranger in a Strange Land: Old Chair, New University

There are opportunities and challenges associated with appointing a chair from within and from outside the organization. This discussion will consider multiple aspects and focus on considerations for changing institutions to assume the chair position

The Isolation, Culture, and Cryopreservation of Human Rectus Sheath Fibroblasts

The vast majority of pelvic and intra-abdominal surgery is undertaken through at least one incision, through either the linea alba or the rectus sheath. These connective tissue layers are formed from the aponeuroses of the rectus muscles (anterior and posterior rectus sheath) and are vital for the structural integrity of the abdominal wall. Poor healing of these connective tissues after surgery can lead to significant morbidity for patients, who can develop unsightly and painful incisional hernias. Fibroblasts within the rectus sheath are responsible for laying down and remodeling collagen during the healing process after surgery. Despite their importance for this healing process, such cells have not been studied in vitro. In order to carry out such work, researchers must first be able to isolate these cells from human tissue and culture them successfully so they may be used for experimentation. This article provides an extensive and detailed protocol for the isolation, culture, cryopreservation, and thawing of human rectus sheath fibroblasts (RSFs). In our hands, this protocol develops confluent cultures of primary fibroblasts within 2 weeks, and sufficient cultures ready for freezing and storage after a further 2 to 4 weeks. © 2023 The Authors. Current Protocols published by Wiley Periodicals LLC. Basic Protocol: Collagenase digestion of human rectus sheath and isolation of RSFs Alternate Protocol: Collagenase digestion of human rectus sheath and isolation of RSFs, digestion in flask Support Protocol: Cryopreservation and thawing of human RSFs