Exploring the Charge Density Wave Phase of 1T-TaSe_{2}: Mott or Charge-Transfer Gap?

1T-TaSe_{2} is widely believed to host a Mott metal-insulator transition in the charge density wave (CDW) phase according to the spectroscopic observation of a band gap that extends across all momentum space. Previous investigations inferred that the occurrence of the Mott phase is limited to the surface only of bulk specimens, but recent analysis on thin samples revealed that the Mott-like behavior, observed in the monolayer, is rapidly suppressed with increasing thickness. Here, we report combined time- and angle-resolved photoemission spectroscopy and theoretical investigations of the electronic structure of 1T-TaSe_{2}. Our experimental results confirm the existence of a state above E_{F}, previously ascribed to the upper Hubbard band, and an overall band gap of ∼0.7 eV at Γ[over ¯]. However, supported by density functional theory calculations, we demonstrate that the origin of this state and the gap rests on band structure modifications induced by the CDW phase alone, without the need for Mott correlation effects.

80% Valley Polarization of Free Carriers in Singly Oriented Single-Layer WS_{2} on Au(111).

We employ time- and angle-resolved photoemission spectroscopy to study the spin- and valley-selective photoexcitation and dynamics of free carriers at the K[over ¯] and K[over ¯]^{'} points in singly oriented single-layer WS_{2}/Au(111). Our results reveal that in the valence band maximum an ultimate valley polarization of free holes of 84% can be achieved upon excitation with circularly polarized light at room temperature. Notably, we observe a significantly smaller valley polarization for the photoexcited free electrons in the conduction band minimum. Clear differences in the carrier dynamics between electrons and holes imply intervalley scattering processes into dark states being responsible for the efficient depolarization of the excited electron population.

Adolescent suicidal ideation.

Adolescent suicidal ideation and its relationship to other variables was tapped by a self-report questionnaire administered to 88 high school seniors. Eighteen percent responded positively to the statement "sometimes I feel suicidal." Those who reported suicidal ideation were found to differ from those who did not on a number of variables, including family relationships (quality of relationship with mother, intimacy with parents, and closeness to siblings), family history of depression (maternal depression), peer relations (quality of peer relationships, popularity, and number of friends), emotional well-being (happiness, anger, and depression), drug use (cigarettes, marijuana, and cocaine), and grade point average. Stepwise regression indicated that happiness explained 46% of the variance in suicidal ideation, and number of friends, anger, and marijuana use explained an additional 20%, for a total of 66% of the variance. While 34% of the variance remained unexplained, it is suggested that the questions used to measure these four variables be included in global screenings to identify adolescents at risk for suicidal ideation.

Employment during adolescence is associated with depression, inferior relationships, lower grades, and smoking.

A self-report questionnaire was administered to high school seniors to collect data on the psychological, behavioral, and social aspects of their lives. It was found that employment was associated with (1) greater depression; (2) inferior relationships with parents and best friend, including less time and physical contact with parents; (3) lower grade point average; and (4) smoking.

THE effects of tonic lung inflation on ventilation in the American bullfrog Rana catesbeiana Shaw.

This study was designed to determine whether lung inflation stimulates or inhibits breathing in frogs by examining the effect of tonic lung inflation on the 'fictive' breathing pattern of decerebrate, unidirectionally ventilated bullfrogs. Neural discharge was monitored in the trigeminal nerve as an indication of the frequency and force of contraction of the buccal pump, and in the laryngeal branch of the vagus nerve as an indication of glottal opening, and hence fictive lung ventilation. Based on the temporal coordination of discharge in the trigeminal and vagus nerves during naturally occurring breaths it was possible to characterize the fictive breaths as inflation, deflation or balanced breaths. Increasing lung inflation increased absolute breathing frequency by reducing the duration of apnea between breaths and promoting a change in breathing pattern from no breathing to single breaths, breathing episodes and, finally, to continuous breathing. Associated with this was a decrease in the amplitude and area of the integrated trigeminal electroneurogram associated with the lung breaths, indicative of a reduction in the force of the buccal pump, and a shift in the timing of the trigeminal and vagal discharge, indicative of a shift from inflation to deflation breaths. Taken together the data suggest that lung deflation produces infrequent, large-amplitude inflation breaths or cycles, but that progressive lung inflation changes the breathing pattern to one of high-frequency attempts to deflate the lungs that are largely passive, and accompanied by contractions of the buccal pump that are no larger than those associated with normal buccal oscillations.

Exercise is positively related to adolescents' relationships and academics.

Eighty-nine high school seniors were administered a questionnaire that gathered information on their exercise habits (ranging from rarely to daily), relationships with parents and peers, depressive tendencies, sports involvement, drug use, and academic performance. Students with a high level of exercise had better relationships with their parents (including greater intimacy and more frequent touching), were less depressed, spent more time involved in sports, used drugs less frequently, and had higher grade point averages than did students with a low level of exercise.

Adolescents' academic expectations and achievement.

Previous research has indicated that adolescents' relationships with their mother influence their academic expectations and achievement. Substance use has also been found to have a strong influence on academic expectations and achievement. In the present study, 80 high school seniors from middle to upper socioeconomic status families completed questionnaires on behavioral and psychological aspects of adolescent life. Academic expectations were found to be highly correlated with academic achievement (r = .60). A stepwise regression analysis revealed that relationship with mother, academic achievement, and alcohol use accounted for 56% of the total variance in academic expectations. Stepwise regression on academic achievement revealed that cocaine use, marijuana use, and academic expectations accounted for 48% of the total variance.

The relationship of Internet use to depression and social isolation among adolescents.

The present study investigated whether higher levels of Internet use are associated with depression and social isolation among adolescents. Eighty-nine high school seniors were administered a questionnaire that measured low (less than 1 hour per day), moderate (1-2 hours per day), and high (more than 2 hours per day) Internet use; relationships with mother, father, and peers; and depression. Low Internet users, as compared with high users, reported better relationships with their mothers and friends.

Angry adolescents who worry about becoming violent.

In the present study, 31 of 89 adolescents responded affirmatively to the following statement: "Sometimes I get so angry that I worry I will become violent." These adolescents (the anger group) were compared with the nonanger group, and several differences were found. The anger group (1) reported less intimacy with parents, received less support from them, and was less close to siblings; (2) had more opposite-sex friends, dated more frequently, and more frequently had a boyfriend or girlfriend; (3) had a lower grade point average; (4) were more depressed; and (5) used marijuana more frequently. Results of a regression analysis revealed that depression and dating were the only significant predictors of anger, explaining 17% of the variance.

Moderate involvement in sports is related to lower depression levels among adolescents.

Sports involvement has been found to be related to social and psychological well-being in Icelandic adolescents. The present study investigated whether similar relationships exist for American adolescents. A group of 89 high school seniors completed a questionnaire that gathered data on sports involvement, depression, intimacy with parents and friends, and grade point average. It was found that the moderate sports involvement group (3 to 6 hours per week) had lower depression scores than did the low sports involvement group (2 hours or less per week). The findings are discussed.

Benefits of continued cyclosporine through an indigent drug program.

Financial circumstances force some stable renal transplant recipients to discontinue cyclosporine (CsA). Previous results from our center document a subgroup of these patients at increased risk for acute rejection and allograft loss, namely, those of African ancestry. After 1988, such disadvantaged recipients have been able to receive CsA at no charge through the National Organization for Rare Disorders (NORD). At the University of Alabama at Birmingham, 54 patients were enrolled in the NORD program between 1988 and 1994. Acute rejection, allograft survival, and patient survival in these patients were compared with those in 42 patients who, prior to 1988, were withdrawn from CsA for financial reasons. Both groups were similar socioeconomically. The mean follow-up was 69 +/- 33 months (+/-SD) in the withdrawal group and 45 +/- 14 months in those entering the NORD program. Acute rejections occurred with similar frequency in both groups before CsA withdrawal (45%) or NORD enrollment (48%). In contrast, acute rejections were more common in patients after the onset of CsA withdrawal (38%) than after NORD enrollment (11%) (P < 0.01). Black patients withdrawn from CsA experienced more acute rejections than their counterparts in the NORD program (57% v 15%) (P < 0.01). White NORD recipients also experienced fewer acute rejections, although the difference was not statistically significant (withdrawal group 16% v NORD group 4%; P = 0.29). Rejection episodes were accompanied by reduced graft survival in black patients withdrawn from CsA, while significant improvement was seen in those remaining on CsA-based therapy (P < 0.05). No difference in allograft survival was seen among white patients in either group (withdrawal group 74% v NORD group 82%; P = 0.33). Thus, long-term access to CsA through the NORD program reduced acute rejections and improved allograft survival in an economically disadvantaged subgroup of renal transplant recipients. These findings emphasize the importance of continued access to CsA in black renal transplant recipients and its influence on long-term allograft survival.

Dilemmas in renal transplantation: when the clinical course and histological findings differ.

Histological examination of renal allograft tissue has become the accepted standard in diagnosing acute rejection. We present three cases of allograft dysfunction in which the histological findings and clinical course differed. Reliance on histology alone in therapeutic decision making might have resulted in inappropriate clinical interventions. In renal transplantation, biopsy results must always be interpreted in conjunction with clinical findings.

Impact of donor/recipient size matching on outcomes in renal transplantation.

Interest in nonimmunologic factors affecting longterm graft survival has focused on adequacy of nephron dosing. Body surface are (BSA) is a reliable surrogate for nephron mass. In a retrospective study of 378 primary recipients of paired kidneys from 189 cadaveric donors, we assessed the impact of matching donor and recipient BSA on outcome over 7 years. BSA of donors was 1.82 +/- 0.26 m2. Initially, paired recipients of kidneys from a single donor were divided into two groups. Group 1 included the recipient with the larger BSA of the pair (1.97 +/- 0.17 m2), while group 2 consisted of smaller BSA recipients (1.69 +/- 0.19 m2). Although early function was better in group 2 patients, graft survival at 1 year (77% vs. 79%) and 5 years (54% vs. 55%) was identical between groups, as were most recent serum creatinine levels (2.0 +/- 0.1 vs. 2.1 +/- 0.1 mg/dl). A second analysis divided patients with a functioning allograft at discharge from initial transplant hospitalization (n = 345) into three groups based solely on donor to recipient BSA ratio: the ratio of group A (n = 30) was < or = 0.8, that of group B (n = 255) was between 0.81 and 1.19, and that of group C (n = 51) was > or = 1.2. Graft survival and kidney function over 5 years did not differ among groups. In multivariate analysis of 17 variables, donor:recipient BSA, independent of other risk factors, did not affect risk allograft loss. These data indicate that including nephron mass as a criterion for cadaveric organ allocation is unlikely to improve long-term results in renal transplantation.

Role of hypertension in chronic renal allograft dysfunction.

The damaging effects of essential hypertension and the central role of the kidney in its pathogenesis have long been recognized. Essential hypertension is the second leading cause of end-stage renal disease in the United States, with its prevalence increasing dramatically over the last decade. Similarly, the role of the transplanted kidney in the pathogenesis of hypertension has been demonstrated in animals and humans. Concerns over the inability of immunologic advancements to improve long-term allograft survival have focused attention on nonimmunologic factors, such as hypertension, and its contribution to chronic renal allograft injury. However, the complex nature of post-transplant hypertension has made it difficult to discern if its occurrence is the cause or the consequence of chronic allograft dysfunction. The possibility remains that, in many patients, the two processes are not mutually exclusive and coexist. Regardless, post-transplant hypertension negatively impacts long-term allograft and patient survival. Many questions regarding the etiology, optimal therapy and role of various growth factors in mediating the damaging effects of post-transplant hypertension remain unanswered and should serve as the focus for future studies.

Tapering or discontinuing cyclosporine for financial reasons--a single-center experience.

In patients with primary cadaveric renal transplants and stable allograft function, we assessed the impact of tapering or discontinuing cyclosporine A (CsA) for financial reasons. Forty-two patients whose CsA was discontinued ("no-dose") and 29 patients whose CsA was tapered to 100 to 150 mg/d ("low-dose"; mean, 1.7 mg/kg/d) were examined. Results were compared with 70 age- and race-matched control patients maintained on at least 200 mg/d of CsA (mean, 3.9 mg/kg/d). Follow-up time for all patients averaged 55 +/- 18 months. Late acute rejection episodes occurred more frequently in no-dose than in low-dose (P = 0.017) or control (P = 0.001) patients. In the no-dose group, blacks experienced a greater number of late acute rejections than whites. These late acute rejections often coincided with the discontinuation of CsA and contributed to an increased rate of allograft loss in blacks in the no-dose group compared with black and white controls (P = 0.011). In contrast, no increase in late acute rejection episodes occurred in blacks tapered to low doses of CsA. Black patients who remained on low doses of CsA also exhibited a trend toward allograft survival that was intermediate between that of control and no-dose patients. In those patients who retained functional allografts, mean serum creatinine concentration did not differ between the study groups at the beginning and end of the follow-up period. These findings support continuance of CsA in black primary cadaveric renal transplant patients, even if dosages must be reduced to 100 to 150 mg/d.(ABSTRACT TRUNCATED AT 250 WORDS)

Immunomodulatory effects of procainamide metabolites: their implications in drug-related lupus.

Evidence suggests that N-oxidized metabolites of procainamide may be responsible for the development of lupus-like symptoms associated with procainamide therapy. The human hepatic microsomal metabolism of procainamide has been previously reported to result in formation of the N-hydroxylamine derivative of procainamide (procainamide hydroxylamine [PAHA]). The objective of this study was to examine the effects of PAHA on human lymphocytes and adherent cells (monocytes and macrophages). When incubated with lymphocytes in whole blood, PAHA enhanced the response to mitogen and immunoglobulin secretion at lower concentrations (less than or equal to 4 mumol/L) but suppressed these functions at higher concentrations. The cytotoxic effects were nonselective for T lymphocytes and B lymphocytes and appeared to involve an interaction between PAHA and hemoglobin. When erythrocytes were removed or when hemoglobin was converted to carboxyhemoglobin, the suppressive effects of PAHA on lymphocytes were reduced. PAHA stimulated interleukin-1 production by adherent cells at 25 mumol/L but had no effect at lower concentrations. Superoxide anion release was unaffected by PAHA in "resting" adherent cells. Pretreatment with PAHA (2 mumol/L) diminished superoxide release in response to stimulation by phorbol myristate acetate (PMA) or latex bead phagocytosis but augmented superoxide release when coincubated with PMA or latex. These observations indicate that PAHA produces complex, concentration-dependent interactions with human immunoregulatory cells, and they suggest that the effects of PAHA on lymphocyte function may result from the further oxidation of PAHA by hemoglobin, perhaps to the nitroso form.

State transitions, photosystem stoichiometry adjustment and non-photochemical quenching in cyanobacterial cells acclimated to light absorbed by photosystem I or photosystem II.

Cells of the cyanobacterium Synechococcus 6301 were grown in yellow light absorbed primarily by the phycobilisome (PBS) light-harvesting antenna of photosystem II (PS II), and in red light absorbed primarily by chlorophyll and, therefore, by photosystem I (PS I). Chromatic acclimation of the cells produced a higher phycocyanin/chlorophyll ratio and higher PBS-PS II/PS I ratio in cells grown under PS I-light. State 1-state 2 transitions were demonstrated as changes in the yield of chlorophyll fluorescence in both cell types. The amplitude of state transitions was substantially lower in the PS II-light grown cells, suggesting a specific attenuation of fluorescence yield by a superimposed non-photochemical quenching of excitation. 77 K fluorescence emission spectra of each cell type in state 1 and in state 2 suggested that state transitions regulate excitation energy transfer from the phycobilisome antenna to the reaction centre of PS II and are distinct from photosystem stoichiometry adjustments. The kinetics of photosystem stoichiometry adjustment and the kinetics of the appearance of the non-photochemical quenching process were measured upon switching PS I-light grown cells to PS II-light, and vice versa. Photosystem stoichiometry adjustment was complete within about 48 h, while the non-photochemical quenching occurred within about 25 h. It is proposed that there are at least three distinct phenomena exerting specific effects on the rate of light absorption and light utilization by the two photoreactions: state transitions; photosystem stoichiometry adjustment; and non-photochemical excitation quenching. The relationship between these three distinct processes is discussed.