String and M-theory: answering the critics

Using as a springboard a three-way debate between theoretical physicist Lee Smolin, philosopher of science Nancy Cartwright and myself, I address in layman's terms the issues of why we need a unified theory of the fundamental interactions and why, in my opinion, string and M-theory currently offer the best hope. The focus will be on responding more generally to the various criticisms. I also describe the diverse application of string/M-theory techniques to other branches of physics and mathematics which render the whole enterprise worthwhile whether or not "a theory of everything" is forthcoming.Comment: Update on EPSRC. (Contribution to the Special Issue of Foundations of Physics: "Forty Years Of String Theory: Reflecting On the Foundations", edited by Gerard 't Hooft, Erik Verlinde, Dennis Dieks and Sebastian de Haro. 22 pages latex

Optimally squeezed spin states

We consider optimally spin-squeezed states that maximize the sensitivity of the Ramsey spectroscopy, and for which the signal to noise ratio scales as the number of particles $N$. Using the variational principle we prove that these states are eigensolutions of the Hamiltonian $H(\lambda)=\lambda S_z^2-S_x,$ and that, for large $N$, the states become equivalent to the quadrature squeezed states of the harmonic oscillator. We present numerical results that illustrate the validity of the equivalence

Coexistence of double alternating antiferromagnetic chains in (VO)_2P_2O_7 : NMR study

Nuclear magnetic resonance (NMR) of 31P and 51V nuclei has been measured in a spin-1/2 alternating-chain compound (VO)_2P_2O_7. By analyzing the temperature variation of the 31P NMR spectra, we have found that (VO)_2P_2O_7 has two independent spin components with different spin-gap energies. The spin gaps are determined from the temperature dependence of the shifts at 31P and 51V sites to be 35 K and 68 K, which are in excellent agreement with those observed in the recent inelastic neutron scattering experiments [A.W. Garrett et al., Phys. Rev. Lett. 79, 745 (1997)]. This suggests that (VO)_2P_2O_7 is composed of two magnetic subsystems showing distinct magnetic excitations, which are associated with the two crystallographically-inequivalent V chains running along the b axis. The difference of the spin-gap energies between the chains is attributed to the small differences in the V-V distances, which may result in the different exchange alternation in each magnetic chain. The exchange interactions in each alternating chain are estimated and are discussed based on the empirical relation between the exchange interaction and the interatomic distance.Comment: 10 pages, 11 embedded eps figures, REVTeX, Submitted to Phys. Rev.

Family stories, public silence: Irish identity construction amongst the second-generation Irish in England

Formal narratives of history, especially that of colonial oppression, have been central to the construction of national identities in Ireland. But the Irish diasporic community in Britain has been cut off from the reproduction of these narratives, most notably by their absence from the curriculum of Catholic schools, as result of the unofficial 'denationalisation' pact agreed by the Church in the 19th century (Hickman, 1995). The reproduction of Irish identities is largely a private matter, carried out within the home through family accounts of local connections, often reinforced by extended visits to parent/s 'home' areas. Recapturing a public dimension has often become a personal quest in adulthood, 'filling in the gaps'. This paper explores constructions of narratives of nation by a key diasporic population, those with one or two Irish-born parents. It places particular emphasis on varying regional/national contexts within which such constructions take place, drawing on focus group discussions and interviews for the ESRC-funded Irish 2 Project in five locations — London, Glasgow, Manchester, Coventry and Banbury

RESOLVING UNCERTAINTIES IN FORAMINIFERA-BASED RELATIVE SEA-LEVEL RECONSTRUCTION : A CASE STUDY FROM SOUTHERN NEW ZEALAND

Since the pioneering work of David Scott and others in the 1970s and 1980s, foraminifera have been used to develop precise sea-level reconstructions from salt marshes around the world. In New Zealand, reconstructions feature rapid rates of sea-level rise during the early to mid-20th century. Here, we test whether infaunality, taphonomy, and sediment compaction influence these reconstructions. We find that surface (0–1 cm) and subsurface (3–4 cm) foraminiferal assemblages show a high degree of similarity. A landward shift in assemblage zones is consistent with recent sea-level rise and transgression. Changes associated with infaunality and taphonomy do not affect transfer function-based sea-level reconstructions. Applying a geotechnical modelling approach to the core from which sea-level changes were reconstructed, we demonstrate compaction is also negligible, resulting in maximum post-depositional lowering of 2.5 mm. We conclude that salt-marsh foraminifera are indeed highly accurate and precise indicators of past sea levels

General psychopathology factor and unresolved-disorganized attachment uniquely correlated to white matter integrity using diffusion tensor imaging

Multivariate analysis of psychological dat

Performance evaluation of digital pulse position modulation for wavelength division multiplexing FSO systems impaired by interchannel crosstalk

Wavelength division multiplexing (WDM) has been proposed for fibre, intersatellite, free space and indoor optical communication systems. Digital pulse position modulation (DPPM) is a more power efficient modulation format than on-off keying (OOK) and a strong contender for the modulation of free-space systems. Although DPPM obtains this advantage in exchange for a bandwidth expansion, WDM systems using it are still potentially attractive, particularly for moderate coding levels. However, WDM systems are susceptible to interchannel crosstalk and modelling this in a WDM DPPM system is necessary. Models of varying complexity, based on simplifying assumptions, are presented and evaluated for the case of a single crosstalk wavelength. For a single crosstalk, results can be straightforwardly obtained by artificially imposing the computationally convenient constraint that frames (and thus slots also) align. Multiple crosstalk effects are additionally investigated, for the most practically relevant cases of modest coding level, and using both simulation and analytical methods. In general, DPPM maintains its sensitivity advantage over OOK even in the presence of crosstalk while predicting lower power penalty at low coding level in WDM systems

Rapid decline in estimated glomerular filtration rate in sickle cell anemia: Results of a multicenter pooled analysis

Chronic kidney disease (CKD), typically defined as kidney damage or decreased kidney function for 3 or more months, is common in sickle cell disease (SCD). Increasing evidence suggests that the glomerulopathy of SCD is progressive. CKD is associated with increased mortality in SCD. Based on single center studies, we previously reported on the high prevalence of rapid decline in kidney function, defined as estimated glomerular filtration rate (eGFR) loss >3.0 mL/min/1.73 m2per year, in SCD. In the present study, we further examine rapid eGFR decline in sickle cell anemia, using a pooled analysis of patients to better characterize factors associated with such decline and its association with mortality

The LOFAR Two Meter Sky Survey: Deep Fields, I -- Direction-dependent calibration and imaging

The Low Frequency Array (LOFAR) is an ideal instrument to conduct deep extragalactic surveys. It has a large field of view and is sensitive to large-scale and compact emission. It is, however, very challenging to synthesize thermal noise limited maps at full resolution, mainly because of the complexity of the low-frequency sky and the direction dependent effects (phased array beams and ionosphere). In this first paper of a series, we present a new calibration and imaging pipeline that aims at producing high fidelity, high dynamic range images with LOFAR High Band Antenna data, while being computationally efficient and robust against the absorption of unmodeled radio emission. We apply this calibration and imaging strategy to synthesize deep images of the Boötes and Lockman Hole fields at ∼150 MHz, totaling ∼80 and ∼100 h of integration, respectively, and reaching unprecedented noise levels at these low frequencies of .30 and .23 µJy beam−1 in the inner ∼3 deg2 . This approach is also being used to reduce the LOTSS-wide data for the second data release

Longitudinal study of glomerular hyperfiltration in adults with sickle cell anemia: a multicenter pooled analysis

Glomerular hyperfiltration is common in young sickle cell anemia patients and precedes development of overt kidney disease. In this multicenter pooled cohort, we characterized hyperfiltration and its decline to normal range in adult patients. Glomerular filtration rate (GFR) was estimated using the creatinine-based 2009 CKD-EPI (Chronic Kidney Disease Epidemiology Collaboration) equation omitting race adjustment and the 2021 CKD-EPI equation. Using CKD-EPI–2009, 506 patients had baseline estimated GFR (eGFR) $90 mL/min per 1.73 m2, median age of 24 (interquartile range [IQR], 19-34) years and 5.17 years of follow-up. The prevalence of hyperfiltration (eGFR$140 and $130 mL/min per 1.73 m2 for men and women, respectively) was 38.3%. Using CKD-EPI–2009, baseline hyperfiltration was less likely with older age (odds ratio [OR], 0.78; 95% confidence interval [CI], 0.73-0.83; P, .0001), male sex (OR, 0.32; 95% CI, 0.18-0.58; P 5 .0002), and higher weight (OR, 0.96; 95% CI, 0.94-0.99; P 5 .001). Using CKD-EPI–2021, hyperfiltration was similarly less likely with older age (OR, 0.75; 95% CI, 0.70-0.81; P, .0001), male sex (OR, 0.24; 95% CI, 0.13-0.44; P, .0001), and higher weight (OR, 0.97; 95% CI, 0.95-0.99; P 5 .004). In patients with baseline hyperfiltration, eGFR declined to normal values at a median age of 26.2 years. Using CKD-EPI–2009, this decline was associated with male sex (HR, 2.20; 95% CI, 1.26-3.87; P 5 .006), systolic blood pressure (hazard ratio [HR], 1.02; 95% CI, 1.01-1.04; P 5 .01), and hydroxyurea use (HR, 1.74; 95% CI, 1.002-3.03; P 5 .05). Using CKD-EPI–2021, decline of eGFR to normal was only associated with male sex (HR, 3.39; 95% CI, 2.01-5.69; P, .0001). Decline to normal eGFR range from hyperfiltration occurs earlier in males, those on hydroxyurea, and with higher systolic blood pressure