Selective excitation of homogeneous spectral lines

It is possible, for homogeneously broadened lines, to excite selectively the response signals, which are orders of magnitude narrower than the original lines. The new type of echo, which allows detecting such signals, and the formalism, useful for understanding the phenomenon, as well as the experimental examples from NMR spectroscopy are presented.Comment: 19 pages, 8 figure

Berry's phase for coherent states of Landau levels

The Berry phases for coherent states and squeezed coherent states of Landau levels are calculated. Coherent states of Landau levels are interpreted as a result of a magnetic flux moved adiabatically from infinity to a finite place on the plane. The Abelian Berry phase for coherent states of Landau levels is an analog of the Aharonov- Bohm effect. Moreover, the non-Abelian Berry phase is calculated for the adiabatic evolution of the magnetic field B.Comment: 4 pages, 1 figur

The many faces of multivisceral transplantation

The transplantation of multiple abdominal viscera, including liver-duodenum-pancreas, liver-stomach-duodenum-pancreas and liver-intestine, is being performed with increasing frequency and success. These procedures and other variations are derived from a seldom used multivisceral operation in which all of the foregoing organs are transplanted en bloc. It is described herein how the full multivisceral transplantation and its less extensive derivatives are based on the same principles of procurement, preservation and postoperative management. With all of these multiple organ permutations and with intestinal transplantation alone, management is complicated by inclusion in the grafts of a large lymphoreticular component that is capable of causing graft versus host disease (GVHD). Because of a systematic error in therapeutic philosophy, past efforts have been directed at altering or damaging the lymphoreticular cells by pretreatment of the donor or of the organs with drugs, irradiation or other means. From recent observations, the alternative approach is suggested of keeping these lymphoid depots intact, which then become the site of two way cell traffic after transplantation. With the use of powerful immunosuppression, such as that provided with FK 506, the donor lymphoreticular cells can circulate in the recipient without causing clinical GVHD, and the lymphoreticular cells in the graft become those of the recipient (local chimerism) without causing rejection. Even with avoidance of rejection and GVHD, metabolic interrelations between the grafted organs, and also between the graft organs and retained recipient viscera can affect the fate of the individual transplanted organs or retained recipient organs. The best delineated of these metabolic influences are mediated by the endogenous splanchnic hepatotrophic factors, of which insulin has been the most completely studied. An understanding of these various immunologic and nonimmunologic factors combined with more potent immunosuppression that is now available is sure to stimulate efforts at transplantation of abdominal organs and particularly of the hollow viscera that have resisted such clinical efforts

Origin of lymph node-derived lymphocytes in human hepatic allografts

Hepatic allograft-derived lymph nodes were examined in the post-transplant period on order to determine the origin of lymphocytes and structural elements of the lymph node. Histologic assessment and immunohistochemical studies verified that T-cell infiltration of donor lymph nodes by recipient-derived lymphocytes occurred early in the post-transplant period. These T cells bore T-cell activation markers, e.g. TAC receptor and HLA-DR antigens. In addition, functional analysis demonstrated alloreactive T cells in secondary proliferation assays. The pattern of alloreactivity in these assays was dependent upon the phenotypic make-up (and therefore origin) of the lymphocytes within the lymph node. A gradual shift in predominance of donor-derived lymphocytes to recipient-derived lymphocytes occurred, but even late in the post-transplant course the stromal elements and a residium of lymphocytes within the lymph nodes continued to bear donor HLA antigens. The possible role of these 'passenger' lymphocytes in allograft immunity is discussed

Modelling the sound absorption of panels with tapered elliptic micro-perforations

A theoretical model is developed in the present study to predict the spectral characteristics of the sound absorption of solid panels with tapered elliptic micro-perforations backed by a rigid wall cavity. In the model, plane wave propagation is assumed along the length of the perforation in the presence of a viscous boundary layer at the internal wall of the perforation. End impedances are approximated using results in existing literature. Validation is done using impedance tube measurements. It is confirmed that the present tapered elliptic perforation model can give much better agreement with experimental results than the conventional cylindrical perforation model for all micro-perforation configurations tested. Results also suggest the importance of perforation density in controlling the variation of sound absorption of the panel absorbers upon changes in perforation configurations

Cytomegalovirus infection of the upper gastrointestinal tract following liver transplantation—incidence, location, and severity in cyclosporine- and FK506-treated patients

One hundred and forty randomly selected liver transplant recipients were studied before and after primary orthotopic liver transplantation for the presence or absence of CMV enteritis. Following OLTx, 65 patients were treated with cyclosporine A and 75 were treated with FK506. The two groups were similar with regard to the incidence, location, and outcome of their upper gastrointestinal CMV infection. Prior to OLTx, only one patient had evidence of enteric CMV infection. The incidence of CMV enteritis post-OLTx was 27.7% in the CsA-treated group and 20% in the FK-treated group. During the first posttransplant month, no patient in the FK-treated group developed CMV enteritis, compared with 11.5% of the patients who were treated with CsA (P<0.05). Gastric CMV was found in over 80% of those positive for any organ in either group. In addition to CMV infection of the upper gastrointestinal tract, clinically evident CMV disease involved more nonenteric organs in the CsA-treated group than in the FK-treated group. In the CsA-treated group, CMV-negative patients had a statistically higher 1-year survival rate (100%) than CMV-positive patients (77.8%) (P<0.05). In the FK-treated group, no difference in survival was observed between CMV-positive or CMV-negative cases at 1 year. Of the patients on CsA, 20% received OKT3 for persistent rejection, as compared with 13% in the FK-treated group. The patients receiving both CsA and OKT3 had a higher rate of upper gastrointestinal CMV infection than did FK-treated patients who also received OKT3 therapy (38.5% versus 20%, respectively). Based upon these data, it can be concluded that (1) patients receiving FK have a lower incidence of enteric CMV infection; (2) following OLTx, upper gastrointestinal CMV infection presents later in FK-treated patients; (3) the stomach is the most frequently involved organ in the UGIT; (4) FK-treated liver recipients have less severe enteric CMV infection than do CsA-treated patients; (5) enteric CMV is not a major cause of mortality in liver trans lant recipients; and (6) in patients receiving FK, those who require OKT3 therapy do not appear to be at a greater risk for the development of CMV enteritis than those who do not. © 1992 by Williams & Wilkins