Dynamics of copper-phthalocyanine molecules on Au/Ge(001).

Spatially resolved current-time scanning tunneling spectroscopy combined with current-distance spectroscopy has been used to characterize the dynamic behavior of copper-phthalocyanine (CuPc) molecules adsorbed on a Au-modified Ge(001) surface. The analyzed CuPc molecules are adsorbed in a "molecular bridge" configuration, where two benzopyrrole groups (lobes) are connected to a Au-induced nanowire, whereas the other two lobes are connected to the adjacent nanowire. Three types of lobe configurations are found: a bright lobe, a dim lobe, and a fuzzy lobe. The dim and fuzzy lobes exhibit a well-defined switching behavior between two discrete levels, while the bright lobe shows a broad oscillation band. The observed dynamic behavior is induced by electrons that are injected into the LUMO+1 orbital of the CuPc molecule. By precisely adjusting the tip-molecule distance, the switching frequency of the lobes can be tuned accurately.

Interfering Bloch waves in a 1D electron system.

Using low-temperature scanning tunnelling spectroscopy we have studied the spatial variation of confined electronic states between neighbouring atomic chains on a Ge(001)/Pt surface. The quasi-one-dimensional electronic states reside in the troughs between the atomic chains and exhibit a profound Bloch character along the chain direction. In the proximity of defects an enhancement of the oscillatory standing wave pattern in the density of states is found. The spatial variation of the standing wave pattern can be explained by an interference of incoming and reflected Bloch waves.

Controlled transport through a single molecule.

We demonstrate how an electrode-molecule-electrode junction can be controllably opened and closed by careful tuning of the contacts' interspace and voltage. The molecule, an octanethiol, flips to bridge a ~1 nm interspace between substrate and scanning tunnelling microscope tip when an electric field exceeds a threshold (switch 'on'). Reducing the field below this threshold value leads to the reproducible detachment of the octanethiol (switch 'off'). Once contacted, a further reduction of the contacts' interspace leads to an increase of the conductance of the molecule.

The basicranium of Plio-Pleistocene hominids as an indicator of their upper respiratory systems.

Our analyses of extant primates have shown that a relationship exists between the degree of flexion of the basicranium and the location of upper respiratory structures such as the larynx and pharynx (Laitman et al., 1978). Based upon these relationships, we have previously used the basicrania of late Pleistocene hominids as a guide to the reconstruction of their upper respiratory anatomy (Laitman et al., 1979). This study continues our approach by examining the basicrania of Plio-Pleistocene hominids and reconstructing their upper respiratory systems. Nine Plio-Pleistocene hominids had basicrania complete enough to be used in this study. These included the originals of Sts 5, MLD 37/38, SK 47, SK 48, SK 83, Taung, KNM-ER 406, OH 24, and a cast of OH 5. Craniometric analysis of the basicrania of these specimens showed that they had marked similarities to those of extant pongids. These basicranial similarities between Plio-Pleistocene hominids and extant apes suggest that the upper respiratory systems of these groups were also alike in appearance. As with living nonhuman primates, the early hominids probably exhibited a larynx and pharynx positioned high in the neck. This high position would have permitted an intranarial epiglottis to be present during both normal respiration and the ingestion of a liquid bolus of food. The high position of the larynx would have also greatly restricted the supralaryngeal portion of the pharynx available to modify laryngeal sounds. It is thus possible that the Plio-Pleistocene hominids exhibited modes of breathing, swallowing and vocalizing similar to those of living apes.

Familial pattern and transmission of Gilles de la Tourette syndrome and multiple tics.

Fifty-two patients with Gilles de la Tourette syndrome (TS) diagnosed according to DSM-lll criteria and/or their parents were interviewed regarding symptoms among family members. Occurrences of TS and multiple tics (MT) among first-degree relatives were distinguished to determine the familial patterns of the two diagnoses. comparing these data with family data collected on a random national sample of patients with TS, we found no differences between the two samples. Each separately and both combined showed that (1) MT seems to be a mild form of TS; (2) both MT and TS are transmitted in the same families; (3) the sex difference is real and not an artifact of ascertainment; and (4) the sex difference is related the the transmitted susceptibility as a threshold effect. A specific genetic mechanism has not been identified.

Familial patterns and possible modes of inheritance of primary affective disorders.

A logistic model was used to analyze the pattern of affected relatives of probands with primary affective disorders (PAD). The sample consisted of 242 patients, diagnosed as either unipolar (UP, 107) or bipolar (BP, 135) and 430 control nonpsychiatric inpatients and all first degree relatives of both groups. Age correction was applied to both groups. The analysis showed a significant baseline increase in frequency of PAD among relatives of PAD probands with siblings more likely to be affected than parents. The difference in frequency of PAD according to sex of relative almost reached significance. Specific diagnosis (UP or BP) of proband did not significantly affect the probability of relatives becoming ill. Genetic models incorporating sex-specific thresholds were able to explain the data satisfactorily as resulting from either Single-Major-Locus inheritance or Multifactorial-Polygenic inheritance.

Hand usage in a colony of bonnet monkeys, Macaca radiata.

Handedness and its possible inheritance have been studied in a colony of 69 Macaca radiata by observation of hand usage during daily feeding and foraging activities. Each animal was observed for the number of right- and left-handed actions made during two tasks:feeding and searching. Individual animals fell into one of three classes: significantly right-handed, significantly left-handed, and no significant preference. For analysis, handedness was considered as both a directional phenomenon (percentage right-handed usage) and a degree phenomenon (absolute deviation from 50:50 hand usage). Feeding and searching were significantly correlated for both direction and degree. Therefore, laterality for handedness does exist in this primate species. A developmental aspect to laterality was suggested by the positive correlation of degree with age. No mother-offspring correlations were found for either direction or degree and half-sibships were not more similar for either. Thus, there is no evidence for a genetic component to either direction or degree of handedness.

Vertical transmission of susceptibility to stuttering with sex-modified expression.

Stuttering is not usually considered genetic, although it has long been known to be familial. Data collected on 2035 relatives of 397 unrelated adult stutterers confirm and quantify the strong familial concentration. Our analytic approach to these family data, one that does not require specification of a genetic hypothesis, shows that stuttering among relatives occurs in a pattern indicating vertical transmission of a susceptibility to stuttering with sex-modified expression. Although simple Mendelian hypotheses are not sufficient to explain the observed pattern of stuttering in families, more complex genetic models can explain the pattern. In the past, such evidence has been considered sufficient, because it does not preclude the possibility of cultural transmission. However, certain cultural transmission hypotheses previously proposed for stuttering are excluded by these data. The findings in this study support a growing opinion among speech pathologists that most stuttering is a genetically inherited neurologic disorder.

Familial stuttering patterns are not related to one measure of severity.

The possibility of a genetic component to the severity of stuttering was investigated using data on 184 adult stutters and their families. Frequency of stuttering during a pre-treatment oral reading task was used as the severity measure for each of the index cases. Information on whether or not a relative ever stuttered was obtained on all first degree relatives. The family data variables, including sex and exact relationship, combined with birthdate and sex of index case were used in three types of analyses: multiple regressions, AID regressions, and stepwise regressions. None of the variables tested, including stuttering among first degree relatives, was a predictor of severity of stuttering in the index case. We conclude that this measure of severity is not related to the genetic factors which predispose to stuttering.

Estimating age-of-onset distributions for disorders with variable onset.

A necessary item of information in many genetic analysis of complex disorders with late onset is the cumulative probability of onset by a given age. The effect of sample design upon the estimation of age-of-onset probability distribution parameters is discussed. Mathematical descriptions of several common sample designs used to estimate the distribution parameters are developed here. Failure to describe the sample space adequately can lead to erroneous genetic analyses because the cumulative probability of onset is incorrectly estimated. In genetic counseling, the errors would usually result in an underestimate of the true risk.