Search

We present computational results associated with the onset of a spin-dependent optical force component occurring on zinc oxide nanowires trapped in optical tweezers with circularly polarized light. This type of non-conservative force appears directed perpendicularly with respect to the propagation direction of the incident light on the nanowires both for plane wave illumination and for optical tweezers. We show how this transverse optical force component is also shape dependent and connected with the imaginary part of the local Poynting vector and the local spin density.

Purpose To assess bladder spatial-dose parameters predicting acute urinary toxicity after radiotherapy for prostate cancer (PCa) through a pixel-wise method for analysis of bladder dose-surface maps (DSMs). Materials & methods The final cohort of a multi-institutional study, consisting of 539 patients with PCa treated with conventionally (CONV:1.8–2 Gy/fr) or moderately hypo-fractionated radiotherapy (HYPO:2.2–2.7 Gy/fr) was considered. Urinary toxicity was evaluated through the International Prostate Symptoms Score (IPSS) administered before and after radiotherapy. IPSS increases ⩾10 and 15 points at the end of radiotherapy (ΔIPSS ⩾ 10 and ΔIPSS ⩾ 15) were chosen as endpoints. Average DSMs (corrected into 2 Gy-equivalent doses) of patients with/without toxicity were compared through a pixel-wise method. This allowed the extraction of selected spatial descriptors discriminating between patients with/without toxicity. Previously logistic models based on dose-surface histograms (DSH) were considered and replaced with DSM descriptors. Discrimination power, calibration and log-likelihood were considered to evaluate the impact of the inclusion of spatial descriptors. Results Data of 375/539 patients were available. ΔIPSS ⩾ 10 was recorded in 76/375 (20%) patients, while 30/375 (8%) experienced ΔIPSS ⩾ 15. The posterior dose at 12 mm from the bladder base (roughly corresponding to the trigone region) resulted significantly associated to toxicity in the whole/HYPO populations. The cranial extension of the 75 Gy isodose along the bladder central axis was the best DSM-based predictor in CONV patients. Multi-variable models including DSM descriptors showed better discrimination (AUC = 0.66–0.77) when compared to DSH-based models (AUC = 0.58–0.71) and higher log-likelihoods. Conclusion DSMs are correlated with the risk of acute GU toxicity. The incorporation of spatial descriptors improves discrimination and log-likelihood of multi-variable models including dosimetric and clinical parameters.

Context. To date, several complex organic molecules have been detected in the interstellar medium, and they have been suggested as precursors of biologically important species. Propargylamine (HC ≡C−CH2−NH2) is structurally similar to a number of other organic molecules which have already been identified by radioastronomy, making it a good candidate for astrophysical detection. Aims. This work provides accurate rest frequencies of propargylamine, from the centimeter-wave to the submillimeter-wave region, useful to facilitate the detection of this molecule in the interstellar medium. Methods. An extensive laboratory study of the rotational spectrum of propargylamine has been performed using a pulsed-jet Fourier Transform Microwave (FTMW) spectrometer (7–19 GHz frequency range) and a frequency modulation microwave spectrometer (75–560 GHz). Several hundred rotational transitions of propargylamine were recorded in the ground and three lowest excited vibrational states. The experiments were supported by high-level ab initio computations, mainly employed to characterize the vibrational state structure and to predict spectroscopic parameters unknown prior to this study. Results. The measured transition frequencies yielded accurate rotational constants and the complete sets of quartic and sextic centrifugal distortion constants for propargylamine in its vibrational ground state. 14N-nuclear quadrupole coupling constants were also determined. Rotational and quartic centrifugal distortion constants were also obtained for the low-lying excited states v13 = 1 (A′), v20 = 1 (A″), and v21 = 1 (A″). The a-type Coriolis resonance which couples the v13 = 1 and v21 = 1 levels was analyzed. Conclusions. The determined spectroscopic constants allowed for the compilation of a dataset of highly accurate rest frequencies for astrophysical purposes in the millimeter and submillimeter regions with 1σ uncertainties that are smaller than 0.050 MHz, corresponding to 0.03 km s−1 at 500 GHz in radial equivalent velocity.

C-cyanomethanimine (HNCHCN), existing in the two $Z$ and $E$ isomeric forms, is a key prebiotic molecule, but, so far, only the $E$ isomer has been detected toward the massive star-forming region. Sagittarius B2(N) using transitions in the radio wavelength domain. With the aim of detecting HNCHCN in Sun-like-star forming regions, the laboratory investigation of its rotational spectrum has been extended to the millimeter-/submillimeter-wave (mm-/submm-) spectral window in which several unbiased spectral surveys have been already carried out. High-resolution laboratory measurements of the rotational spectrum of C-cyanomethanimine were carried out in the 100-420 GHz range using a frequency-modulation absorption spectrometer. We then searched for the C-cyanomethanimine spectral features in the mm-wave range using the high-sensitivity and unbiased spectral surveys obtained with the IRAM 30-m antenna in the ASAI context, the earliest stages of star formation from starless to evolved Class I objects being sampled. For both the $Z$ and $E$ isomers, the spectroscopic work has led to an improved and extended knowledge of the spectroscopic parameters, thus providing accurate predictions of the rotational signatures up to $\sim$700 GHz. So far, no C-cyanomethanimine emission has been detected toward the ASAI targets, and upper limits of the column density of $\sim$ 10$^{11}$--10$^{12}$ cm$^{-2}$ could only be derived. Consequently, the C-cyanomethanimine abundances have to be less than a few 10$^{-10}$ for starless and hot-corinos. A less stringent constraint, $\leq$ 10$^{-9}$, is obtained for shocks sites. The combination of the upper limits of the abundances of C-cyanomethanimine together with accurate laboratory frequencies up to $\sim$ 700 GHz poses the basis for future higher sensitivity searches around Sun-like-star forming regions., 9 pages, 4 figures, 2 tables. A&A accepted

The submillimetre-wave spectrum of C3 O( X 1 Σ + ) has been investigated in the laboratory using a source-modulation microwave spectrometer equipped with a gas-phase flow pyrolysis system for the production of unstable chemical species. C3O was produced by thermal decomposition of fumaryl chloride at 900 ◦ C. Thirty-seven new rotational transitions were observed in the frequency range 307–740 GHz for the ground vibrational state, reaching a J quantum number as high as 76. Additionally, new millimetre-wave and submillimetre-wave lines were recorded for the bending fundamental v5 = 1, and for its overtones v5 = 2a ndv5 = 3 whose rotational spectra have been identified for the first time. The new laboratory measurements provide much improved rest frequencies in the submillimetre spectral region for the ground state spectra of C3O, and for the first levels of its low-energy v5 vibrational ladder, useful for the radioastronomical identification of their rotational lines in the ISM.

The ground-state rotational spectrum of HCO+, produced in a negative-glow discharge cell, has been recorded up to 892 GHz. The sources of systematic error have been carefully accounted for, thus obtaining accurate rotational and centrifugal distortion constants. The present measurements have allowed us to determine a value of the sextic distortion constant, HJ, which, unlike the recent determination of Lattanzi et al., is consistent with the values determined for DCO+ and for the isoelectronic molecule HCN. The new set of spectroscopic constants allows us to predict the rotational spectrum of the formyl ion with an accuracy of 1 part in 10^8 near 1 THz. Such an accuracy is important for kinematic studies of dense cores in molecular clouds and for future far-infrared observations.

Normal and deuterated isotopic variants of thioborine have been produced in the gas phase by a high temperature reaction between crystalline boron and hydrogen sulfide. Millimeter- and submillimeter-wave rotational spectra have been recorded in the frequency range from 75 to 730 GHz for vibrational ground and excited states of the H 10/11 B 32 S and D 10/11 B 32 S isotopic species. The spectra of all the excited states which lie below 1500 cm −1 , that are 01 1 0, 00 0 1, 02 0 0, and 02 2 0, have been observed and analyzed for each of the four isotopologues investigated. High-order Fermi resonance parameters were found important to analyze properly the spectra of the 00 0 1 and 02 0 0 interacting states. The improved rotational data in conjunction with earlier infrared spectroscopy results have been employed to calculate more precise anharmonic force constants and equilibrium bond lengths.

Pure rotational transitions of silicon monosulfide ((28)Si(32)S) and its rare isotopic species have been observed in their ground as well as vibrationally excited states by employing Fourier transform microwave (FTMW) spectroscopy of a supersonic molecular beam at centimetre wavelengths (13-37 GHz) and by using long-path absorption spectroscopy at millimetre and submillimetre wavelengths (127-925 GHz). The latter measurements include 91 transition frequencies for (28)Si(32)S, (28)Si(33)S, (28)Si(34)S, (29)Si(32)S and (30)Si(32)S in upsilon = 0, as well as 5 lines for (28)Si(32)S in upsilon = 1, with rotational quantum numbers J''or = 52. The centimetre-wave measurements include more than 300 newly recorded lines. Together with previous data they result in almost 600 transitions (J'' = 0 and 1) from all twelve possible isotopic species, including (29)Si(36)S and (30)Si(36)S, which have fractional abundances of about 7 x 10(-6) and 4.5 x 10(-6), respectively. Rotational transitions were observed from upsilon = 0 for the least abundant isotopic species to as high as upsilon = 51 for the main species. Owing to the high spectral resolution of the FTMW spectrometer, hyperfine structure from the nuclear electric quadrupole moment of (33)S was resolved for species containing this isotope, as was much smaller nuclear spin-rotation splitting for isotopic species involving (29)Si. By combining the measurements here with previously published microwave and infrared data in one global fit, an improved set of spectroscopic parameters for SiS has been derived which include several terms describing the breakdown of the Born-Oppenheimer approximation. With this parameter set, highly accurate rotational frequencies for this important astronomical molecule can now be predicted well into the terahertz region.

Purpose To develop a modelling procedure for late rectal bleeding (LRB) that goes beyond maximum likelihood model fitting of data. Thus, to create a metamodel for grade 2–3 (G23) and grade 3 (G3) LRB starting from literature evidence and validate it on a large population. Methods Metamodelling allows to highlight specific features of the model itself. Characteristics that predictive models for LRB have in common are: the global harmony of radiobiological parameters (volume effect parameter, n, steepness of the curve, k, and dose parameter associated to 50% of complication probability, D50) and specific clinical factors that frequently occur. Models including rectal Equivalent Uniform Dose (EUD) with/without patient-related dose-modifying factors (DMF) were retrieved by literature search. Dosimetric coefficients were resolved by weighted mean of published values, using their standard deviation as weight. Identified clinical features, expressed by DMF, were differently weighted taking into account the prevalence of the features and the size of the study. Finally, both factors were inserted in a modified logit-EUD model. Metamodel was validated on a pooled population (3DCRT/IMRT) of three international cohorts. Performance was assessed through calibration. Results Literature search identified rectal EUD, previous abdominal surgery, hormone therapy and use of cardiovascular drugs as relevant features: associated coefficients are presented in Table 1 . Validation cohort included 1591 pts with 240 (15%) LRBG23 and 98 (6.2%) LRBG3 pts. The calibration (Fig. 1) showed the following results: concerning LRBG23 the slope was equal to 0.22 (R2 = 0.38); the corresponding values for LRBG3 were 1.12 and 0.97. Conclusions A metamodel for prediction of LRB was derived from literature. LRBG3 model was successfully validated on a large population proving to be a valuable tool for predicting toxicity before RT. The model for LRBG23 predicted very well toxicity rate below 25% (which involved 87% of the population) while partially failing at higher probabilities.

Motivated by field-theoretic predictions we investigate the stable excitations that exist in two characteristic gapped phases of a spin-1 model with Ising-like and single-ion anisotropies. The sine-Gordon theory indicates a region close to the phase boundary where a stable breather exists besides the stable particles, that form the Haldane triplet at the Heisenberg isotropic point. The numerical data, obtained by means of the Density Matrix Renormalization Group, confirm this picture in the so-called large-D phase for which we give also a quantitative analysis of the bound states using standard perturbation theory. However, the situation turns out to be considerably more intricate in the Haldane phase where, to the best of our data, we do not observe stable breathers contrarily to what could be expected from the sine-Gordon model, but rather only the three modes predicted by a novel anisotropic extension of the Non-Linear Sigma Model studied here by means of a saddle-point approximation., Comment: 8 pages, 7 eps figures, svjour class

The submillimetre-wave spectrum of the SiN radical has been investigated in the laboratory using a source-modulation microwave spectrometer equipped with a negative glow discharge cell. SiN was produced in a SiCl4/N2 discharge plasma. Twenty-one new fine and hyperfine components up to N = 17−16 were observed reaching a frequency as high as 740 GHz. The new laboratory measurements provide much improved rest frequencies in the submillimetre spectral region useful for the identification of SiN lines in hot core sources and circumstellar shells.

The rotational spectra of 28SiF2, 29SiF2, and 30SiF2 in their ground vibrational states, as well as those of 28SiF2 in the v1 = 1, v2 = 1, v3 = 1, and v2 = 2 excited states have been studied in selected frequency regions between 80 and 700 GHz. Transitions involving a large range of quantum numbers have been observed, so that precise rotational and quartic centrifugal distortion constants could be determined for each of the spectra investigated. In addition, the complete set of sextic distortion constants was also obtained for the most abundant isotopomer in its ground vibrational state. The quadratic and cubic force constants of silicon difluoride have been refined by a least-squares procedure using a larger and more precise set of data.

The semistable FCP molecule has been produced in the gas phase by a high temperature reaction between phosphine and trichlorofluoromethane. Its rotational spectrum has been observed in the millimetre- and submillimetre-wave regions, from 80 to 650 GHz, for the ground and various vibrationally excited states of F12CP, and for the ground state of F13CP. All the excited states that lie below 1200 cm-1, which are 1000, 01^10, 02^00, 02^20, 03^10, 03^30, and 11^10, have been investigated for the most abundant isotopologue. The analysis of the spectra has been performed taking simultaneously into account the strong Fermi resonance that couples the states v1, v2, v3 with v1-1, v2+2, v3, and l-type resonances between different sublevels of a given bending state, in order to obtain directly deperturbed rotational parameters. CCSD(T) calculations with a series of correlation consistent basis sets have been also performed, which provided a reliable estimate of the quartic force field of fluorophosphaethyne. Effects due to truncation of the basis and to core correlation have been accounted for. The theoretical force field has been partly refined by a least-squares fit to the available vibrational and rotational experimental data. A mixed experimental–theoretical equilibrium structure has been finally calculated combining experimental ground-state rotational constants of F12CP and F13CP with computed zero-point contributions. The best estimate of the equilibrium structure of fluorophosphaethyne can be established as re(F-C)=1.2759+/-0.0004 A and re(C-P)=1.5445+/-0.0002 A.

The rotational spectrum of HC5N has been investigated in the millimeter-wave region, from 60 to 290 GHz, for 15 vibrationally excited states which lie approximately between 500 and 860 cm−1, namely (v6 v7 v8 v9 v10 v11) = (000005), (000006), (000007), (000008), (000020), (000030), (001000), (010000), (100000), (000021), (000101), (001001), (010001), (000110), and (001010). Gas-phase copyrolysis of pyridine and phosphorus trichloride or, alternatively, a dc discharge in a gaseous mixture of vinyl cyanide and acetylene were used to produce the semi-stable HC5N molecule. A large number of vibrational and rovibrational interactions has been taken into account to fit properly the measured transition frequencies of the states investigated. The most important perturbations are caused by the high-order Coriolis resonances observed between the (v8, v10) and (v8 − 1, v10 + 2) states, and between the (v7, v10, v11) and (v7 − 1, v10 + 3, v11 − 1) states, and by the cubic anharmonic interactions which mix the (v6, v8, v11) states with the (v6 − 1, v8 + 1, v11 + 1) states, and the (v6, v10) states with the (v6 − 1, v10 + 2) states. The analysis of the spectra was facilitated by CCSD(T) calculations with the cc-pVQZ basis, which provided accurate predictions of a large variety of spectroscopic constants like harmonic vibrational wavenumbers, vibration–rotation coupling constants, l-type doubling constants, and normal-coordinate cubic force constants. Excellent agreement between experiment and theory was generally observed, even when the experimental data were strongly perturbed by resonance effects.

The carbon chain HC7N has been produced in the laboratory by gas-phase copyrolysis of phosphorus trichloride and 2-ethynyl-pyridine (C7H5N). Its rotational spectrum has been investigated in the millimeter-wave region for the ground state and for five vibrationally excited states that lie below 300 cm-1, namely, (v13,v14,v15) = (0, 0, 1), (0, 0, 2), (0, 0, 3), (0, 1, 0), and (1, 0, 0). Transitions up to J = 201 ← 200 were observed for the ground vibrational state, reaching a frequency as high as 230 GHz. The laboratory assignment of the rotational spectra of HC7N in low-lying vibrational states provides accurate rest frequencies useful for a possible identification of radio lines produced by vibrationally excited HC7N in hot core molecular sources and circumstellar shells.

Context. Diacetylene, C4H2, has been identified in several astronomical environments through its infrared spectrum. In contrast, monodeuterated diacetylene (DC4H) has not been detected in space so far owing to the low isotopic abundance of deuterated species but also to the rather poor laboratory spectroscopic characterisation of this molecule. Aims. The aim of this work is to provide accurate spectroscopic parameters for DC4H to achieve reliable predictions for both its spectra at millimetre and infrared wavelengths. Methods. We studied the rotational spectrum of DC4H in the range 85–615 GHz by millimetre-wave spectroscopy and the infrared spectrum below 1000 cm −1 by high-resolution, Fourier-transform spectroscopy. Several pure rotational transitions were recorded in the ground state and in excited vibrational bending states. The three fundamental bands v6, v7 ,a ndv8 have been identified and assigned in the infrared spectrum. Results. The rotational transitions were analysed together with the infrared data in a global fit that produces very accurate rovibrational parameters. The observed frequencies and wavenumbers are reported to provide precise guidance for astronomical searches.

Rotational transitions of 12C2HD were recorded in the range 100–700 GHz for the vibrational ground state and for the bending states v4 = 1 (Π), v5 = 1 (Π), v4 = 2 (Σ+ and Δ), v5 = 2 (Σ+ and Δ), v4 = v5 = 1 (Σ−, Σ+ and Δ), v4 = 3 (Π and Φ) and v5 = 3 (Π and Φ). The transition frequencies measured in this work were fitted together with all the infrared ro-vibrational transitions involving the same bending states available in the literature. The global fit allowed a very accurate determination of the vibrational, rotational, and ℓ-type interaction parameters for the bending states up to v4 + v5 = 3 of this molecule. The results reported in this paper provide a set of information very useful for undertaking astronomical searches in both the mm−wave and the infrared spectral regions. The parameters from the global fit can be used to calculate accurate rest frequencies for rotational transitions in the ground state or in excited vibrational states involving the bending modes. Pure rotational transition frequencies up to 1 THz are listed.

The high-resolution infrared spectrum of monodeuterated diacetylene has been recorded in the 450-1100 cm(-1) spectral region by Fourier transform infrared spectroscopy. Seven new bands have been identified: the ν3 fundamental (C-C stretch), and the ν8 + ν9, ν7 + ν8, 2ν7, 2ν8, ν8 + ν9 - ν9, and ν6 + ν9 - ν9 combination, overtone, and hot bands. The assigned transitions, together with those previously reported for the fundamental bands [F. Tamassia, L. Bizzocchi, C. Degli Esposti, L. Dore, M. Di Lauro, L. Fusina, M. Villa, and E. Canè, Astron. Astrophys. 549, A38 (2013)], form a comprehensive data set which comprises more than 2500 ro-vibrational transitions, and involves all singly and most doubly excited vibrational states of DC4H lying below 1000 cm(-1). Rotational and vibrational l-type resonance effects among the sub-levels of excited bending states were considered in the analysis, which also included a careful treatment of the various anharmonic interactions coupling many vibrational states lying above 600 cm(-1). Reliable and unambiguous spectroscopic parameters were obtained for each investigated state, including the rotational and centrifugal distortion constants Bv and Dv, the l-type doubling parameter qt, the anharmonicity constants xL(89), xL(69), and the vibrational l-type terms r89, r69 for the v8 = v9 = 1 and v6 = v9 = 1 bend-bend combination states.

The question of how network topology influences emergent synchronized oscillations in excitable media is addressed. Coupled van der Pol-FitzHugh-Nagumo elements arranged either on regular rings or on clusters of the square lattice are investigated. Clustered and declustered rings are constructed to have the same number of next-nearest-neighbors (four) and a number of links twice that of nodes. The systems are chosen to be close-to-threshold, allowing global oscillations to be triggered by a weak diversity among the constituents that, by themselves, would be non-oscillating. The results clearly illustrate the crucial role played by network topology. In particular we found that network performance (oscillatory behavior and synchronization) is mainly determined by the network average path length and by the standard deviation of path lengths. The shorter the average path length and the smaller the standard deviation, the better the network performance. Local properties, as characterized by the clustering coefficient, are less important. In addition we comment on the mechanisms that sustain synchronized oscillations and on the transient times needed to reach these stationary regimes., 11 pages and 13 figures

Context. Methanimine (CH2NH) has been detected in different astronomical sources, both galactic (as in several “hot cores”, the circumstellar enevolope IRC+10216, and the L183 pre-stellar core) and extragalactic, and is considered a pre-biotic interstellar molecule. Its ground-state rotational spectrum has been studied in the laboratory up to 172 GHz, well below the spectral ranges covered by Herschel/HIFI and the ALMA bands 9 and 10. Aims. In this laboratory study, we extend into the submillimetre-wave region the detection of the rotational spectrum of CH2NH in its vibrational ground state. Methods. The investigation was carried out using a source-modulation microwave spectrometer equipped with a cell coupled to a pyrolysis apparatus working at 1150 ◦ C. The spectrum was recorded in the frequency range 329–629 GHz, with the detection of 58 transitions. Results. The newly measured transition frequencies, along with those available from previous microwave studies, allow us to determine fairly accurate rotational constants of CH2NH and the complete sets of quartic and sextic centrifugal distortion constants, in addition to two octic constants. Several transitions have an hyperfine structure due to the 14 N nucleus, which was accounted for in the analysis. Conclusions. The determined spectroscopic constants make it possible to build a list of very accurate rest-frequencies for astrophysical purposes in the THz region with 1σ uncertainties lower than 0.01 km s −1 in radial equivalent velocity.

The weak 2 ν 3 overtone band of the three isotopomers of cyanogen iodide, I 12 C 14 N, I 13 C 14 N, and I 12 C 15 N, has been recorded in the range from 4200 to 4400 cm −1 with a resolution of 0.02 cm −1 using a Fourier transform infrared spectrometer. The following band origins have been determined from the analysis of the spectra: ν 0 (I 12 C 14 N)=4332.8368 cm −1 , ν 0 (I 13 C 14 N)=4235.7355 cm −1 , and ν 0 (I 12 C 15 N)=4274.2851 cm −1 . This allowed us to achieve complete knowledge of the energies for all levels of ICN corresponding to double vibrational excitation. An improved evaluation of the quartic force field of cyanogen iodide has been performed using the new data obtained together with those already known from previous works.

Quantum spin-1 chains may develop massless phases in presence of Ising-like and single-ion anisotropies. We have studied c=1 critical phases by means of both analytical techniques, including a mapping of the lattice Hamiltonian onto an O(2) nonlinear sigma model, and a multi-target DMRG algorithm which allows for accurate calculation of excited states. We find excellent quantitative agreement with the theoretical predictions and conclude that a pure Gaussian model, without any orbifold construction, describes correctly the low-energy physics of these critical phases. This combined analysis indicates that the multicritical point at large single-ion anisotropy does not belong to the same universality class as the Takhtajan-Babujian Hamiltonian as claimed in the past. A link between string-order correlation functions and twisting vertex operators, along the c=1 line that ends at this point, is also suggested.

The unstable NCCCCP molecule has been detected in the pyrolysis products of phosphorus trichloride and ortho-cyanotoluene mixtures. Its rotational spectrum has been investigated in the millimeter and submillimeter-wave regions for the ground and various vibrationally excited states which approximately lie below 400 cm−1, namely (v8,v9)=(0,1),(0,2),(0,3),(0,4),(1,0), and (1,1). Transitions up to J=241←240 were measured for the ground state, making a precise evaluation of the sextic centrifugal distortion constant possible. The l-type resonances between the different sublevels of the bending states have been taken into account in the analysis of the spectra, which yielded accurate determinations of the xL(99) and xL(89) anharmonicity constants.

1-Phosphapropyne has been produced in the gas phase by pyrolysis of a mixture of ethane and phosphorus trichloride. The ground state rotational spectra of the most abundant isotopomer and of the isotopic variants 13 CH 3 CP and CH 3 13 CP have been investigated in the millimeter and submillimeter wave regions obtaining very accurate values of the quartic centrifugal distortion constants D J and D JK and of the sextic distortion constants H JK and H KJ .

We address some open questions regarding the phase diagram of the one-dimensional Hubbard model with asymmetric hopping coefficients and balanced species. In the attractive regime we present a numerical study of the passage from on-site pairing dominant correlations at small asymmetries to charge-density waves in the region with markedly different hopping coefficients. In the repulsive regime we exploit two analytical treatments in the strong- and weak-coupling regimes in order to locate the onset of phase separation at small and large asymmetries respectively., Comment: 13 pages, RevTeX 4, 12 eps figures, some additional refs. with respect to v1 and citation errors fixed